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MIDDLE EAST TECHNICAL UNIVERSITY
CHEMICAL ENGINEERING DEPARTMENT
ChE 418
CHEMICAL ENGINEERING DESIGN I
FINAL REPORT
SUBMIT...
TABLE OF CONTENTS
Abstract
Table of Contents
List of Tables
List of Figures
Nomenclature
1. Introduction 1
2. Design Basis...
Abstract
In this report, design of a dimethyl ether production plant is done by considering, raw materials to use,
equipme...
List of Tables
Table 2.1: Design basis for the dimethyl ether production
Table 7.1. Equipment Schedule Sheet
Table 8.1: Ma...
List of Figures
Figure 1.1: Methods of production
Figure 3.1: Flow diagram of DME production.
Figure 12.2.1 Stoichiometric...
i
NOMENCLATURE
Symbols Definition
Area
Concentration of Species i
Heat Capacity
Diameter
Nominal Inside Diameter
Overall C...
ii
Volume
Catalyst Weight
Drive Power
Shaft Power
Conversion
Greek Symbols
α Relative Volatility
Viscosity
Liquid Density
...
1
1. INTRODUCTION
The production of high purity DME became one of the most important issues of the world
industry in recen...
2
In order to perform this reaction aluminum silicate catalyst is used. Between 250- 400 ˚C it is
suitable for reaction in...
3
2. DESIGN BASIS
Table 2.1: Design basis for the dimethyl ether production
Feed: Methanol
Purity (wt %) – (rest is water)...
4
3. PROCESS FLOW DIAGRAM OF DIMETHYL ETHER PRODUCTION BY METHANOL DEHYDRATION
Figure 3.1: Flow diagram of DME production....
5
4. PROCESS DESCRIPTION
Plant that is considered to be designed, has a capacity to use 60,000 metric tons of DME as a fee...
6
5. PIPELINE DESIGN
In order to find the optimum pipe diameter following equations were used.
For turbulent flow in steel...
7
ρ = fluid density b/ft3
qf = fluid flow rate ft3/s
μ = fluid viscosity lb/ft.s
Pipeline for Stream: 1
Assume that pipe d...
8
=
= = 12078>>> 2100
Nominal size of pipe, in =1/8 Schedule no= 80 , Wall thickness, in = 0.095
Pipeline for stream:4
Ass...
9
=
= = 4354 >>> 2100
Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068
10
Pipeline for Stream : 7
Assume that pipe diameter is greater than 1 in and laminar flow.
3.75
=421 =
= 0.000139
=
= 0.4...
11
= = 1063 <<< 2100
Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068
Pipeline for Stream : 10
A...
12
Pipeline for Stream : 11
Assume that pipe diameter is greater than 1 in and turbulent flow.
55
=73 =
= 9.92*10^-5
= 1.1...
13
6. Layout (Plot Plan)
14
7.1. EQUIPMENT SCHEDULE
Table 7.1. Equipment Schedule Sheet
Item No. No. of
Required
Equipment Name Size(Each)
V-101 3 ...
15
SIEVE TRAY COLUMN SPECIFICATION SHEET
Page 1 of 3
Item No. : T-101 By : Group I
Name : DME Separation Column Date: 20-0...
16
Est. Overall plate efficiency, % 0.39
Calculated plates 9 stages
Page 2 of 2
Column Design:
Materials of construction
C...
17
Tower ID to fit, m
Total tower cross-section area, m
2
Normal tray spacing, m
Number liquid passes
Perforations :
Hole ...
18
m
3
/h
Liquid Ioad, kg/h
m
3
/h
L/V ratio, kg/kg
Properties :
Vapor density, kg/m
3
Liquid density, kg/m
3
Liquid surfa...
19
Downcomer capacity:
Height clear liquid in downcomer,cm
Height froth (Assume Φ=0.5), cm
% downcomer floor
Downcomer res...
20
Operating reflux ratio 1.251
Feed, % vapor Liquid (0% vapor)
Req'd equilibrium stages at oper. reflux
(inc. reboiler )
...
21
Vessel design press., barg.
Wall thickness, cm
Includes corrosion allow., cm
Insulation required (Yes or No)
Tray Desig...
22
Page 3 of 3
Tray Dynamics Calculations : Top Tray Bottom Tray
Pressure, bar g.
Temperature, ºC
Loading:
Vapor load, kg/...
23
Actual Uf, cm/s
Weep Uf, % actual
Mise. dynamic factors
Liquid crest over weir, cm
Liquid gradient
Mean height of froth...
24
8. Economic Evaluation
 Estimate Of Capital Requirements
Table 8.1: Manufacturing Capital
I. Manufacturing Capital
Ite...
25
Table 8.2: Non-Manufacturing Capital Investment
II. Non-Manufacturing Capital Investment
Total
Cost ($)
Proportionate s...
26
Table 8.3: Manufacturıng Cost Sheet
Manufacturıng Cost Sheet
LOCATION: İZMİT
Design: DME Plant per Yr. (8320 h)
Mfg. Ca...
27
Technical service
Royalty
Depreciation ( 8% of Mfg. Cap/year) 338574 0.0079
Factory Indirect Expense ( 4% of Mfg. Cap/y...
28
9. Discussion
The objective of this study is to make preliminary design for a plant which produces DME by
using 60,000,...
29
Silica alumina is an effective catalyst for dehydration reaction of methanol so it is chosen as
catalyst. Weight of cat...
30
stages as 7 and bu hand calculation is found 9. In order to obtain actual number of stage
overall efficiency is calcula...
31
addition, heat integration is applied by using reactor effluent to heat feed in the process to
decrease cost of utility...
32
10. Conclusion
The aim of the project is to make preliminary design for DME production including economic
analysis. One...
33
11. References
[1] Timmerhaus, K. D., Peters, M. S. & West R. E. (2003). Plant Design and Economics for
Chemical Engine...
34
12. Appendices
12.1 Physical and Chemical Properties of methanol and dimethyl ether
 DME from synthesis gas (CO+H2)
2C...
35
12.2 Equilibrium restriction for DME synthesis
Since it is known that methanol synthesis reaction is an equilibrium res...
36
12.3: SAFETY CONSIDERATIONS
Safety is the control of recognized hazards to achieve an acceptable level of risk. It incl...
37
Dot labels required: Flammable gas
Marine pollutant: DME is not classified as a marine pollutant
DME packages: Packages...
38
o FMEA
o FTA
o HAZOP
HAZOP is chosen for this design as the process hazard analysis method since it is the most
widely ...
39
15.3. HAZOP STUDY
Table 15.1. Hazop Study for Reactor
Guide Word Deviation Cause Consequences Action
No No flow -Blocka...
40
As well as -Impurities in feed stream
-Water in recycle system
-Problems in raw material
-Fouling in pipes
-Low convers...
39
12.4: SUSTAINABILITY CONSIDERATIONS
Sustainability is an important consideration for chemical plants and industry. Ever...
40
Heat integration is another important issue to be considered from the environmental point of view
since heating and coo...
41
12.5 : Material and Energy Balance Calculations
OVERALL MATERIAL BALANCE
12.5.1 Input-Output Diagram of the Plant
B
A
C...
42
12.5.2 Overall Material Balances
The calculations are made based on process design basis. Overall process is selected a...
43
MATERIAL AND ENERGY BALANCES FOR REACTOR AND REACTOR FEED
PREPARATION
 Material Balance around Reactor
To make this ca...
44
Table 12.5.2.3 : Explanation of symbols that used in diagram
Symbol Streams
1 Methanol input the reactor
2 Water input ...
45
 Reactor Feed Preparation
Material Balance
Firstly, feed preparation part was considered as a black box. By doing so, ...
46
Balance on species of methanol and water will be as below since there is no reaction in feed
preparation unit:
n1 + n3 ...
47
ΔHvap,water:Latent heat of vaporization of water =40.7 kJ/mol
ΔHvap,meth:Latent heat of vaporization of meth =35.3 kJ/m...
48
12.6 EQUIPMENT DESIGN FOR REACTOR AND REACTOR FEED PREPARATION
Design of Reactor
Synthesis of DME from methanol dehydra...
49
Approaching the problem
The procedure listed below illustrates the design of the packed bed reactor for DME synthesis
f...
50
where;
X : Single pass conversion
FA0: Molar flow rate of methanol
W: Weight of catalyst
ΔHrxn : Heat of reaction
Dp : ...
51
Where;
( )
( ) ( ) ( )
Table 12.6.1 Parameters and its values
Parameter Value
k0(kmol/m3
.cat*h*kPa) 1.21*106
Ea (kJ/mo...
52
 = 4.80 m3
Then by using Eqn 6.1.1-4 and Eq 6.1.1-5, dimension of reactor is found. To apply this relations particle
s...
53
Design of Reactor Feed Preparation
Figure 12.6.1: CHEMCAD simulation for the feed preparation.
Vessel (V-101) (Drum)
Fr...
54
Pump (P-101)
According to design heuristics for pumps that is stated in table 11.9 [3], power for pumping
liquids is de...
55
ChemCad simulation, which is given as report in the Appendix section. Then we can use the general
heat exchanger equati...
56
(6.2.3.1.2)
Table 12.6.2: Description of the first heat exchanger streams and their temperatures
Feed preparation inlet...
57
The second heat is exchanger is designed different than the first one. It uses reactor outlet for
the heating fluidng. ...
58
( ) ( )
According to Heuristics: (table 11.11)[3]
 Due to boiling, pressure drop is chosen 0.1 bar for first heat exch...
59
 Separation Columns:
Separator Feed Preparation Condenser
 Energy balance around Feed Preparation Condenser
According...
60
 Partial reboiler of DME separation column:
The heat duty of the partial reboiler is taken from ChemCad DME Tower simu...
61
 Total condenser of DME separation column:
The heat duty of the total condenser is taken from ChemCad DME Tower simula...
62
 Total condenser of methanol separation column:
The heat duty of the total condenser is taken from ChemCad DME Tower s...
63
 DESIGN OF DISTILLATION TOWERS
i) DME Tower Stage Calculations
There are two distillation columns necessary for the di...
64
7)Then, the reflux ratio (R) is calculated ,in both ways, at the pinch point which is the
intersection point of q-line ...
65
Theoretical stage number ,N, will also be calculated by Kirkbride equation :
6) Determine overall efficiency of column ...
66
2) Light Key (LK) is selected as DME
Heavy Key (HK) is selected as Methanol
3) Relative volatilities with respect to st...
67
Plugging computed data into Gilliland correlation (Wankat,2011) and solving for N
Figure 12.6.5.Gillilan correlation (1...
68
10)
√
11)
69
ii) Methanol Tower Stage Calculations
In methanol tower which is the second separation unit of the dimethyl ether produ...
70
Ym+1 =
( )
( ) ( )
4) Determine R using the common relation between R and Rmin which is;
 (1.2)R min< R < (1.5)Rmin
5)...
71
Calculation of ideal stages:
The number of ideal stages for methanol water separation is determined by using McCabe-
Th...
72
Point 1. at = so, yn+1 = = 0.995
Point 2. at = 0 so, , yn+1 =
( )
= 0.379
Using these two points, the operating line fo...
73
12.7 Cost Calculations including Equipment Cost Data
ECONOMIC ANALYSIS FOR PUMPS
Now, purchased equipment cost can be o...
74
Utility Cost
Estimation for Pumps
All pumps are working with electricity. The price of electricity is given as 0.11 $/k...
75
Height (m) 6.22 18.9
P (bar) 10.4 10.4
Material of
Construction
Carbon
Steel
Carbon
Steel
Tray type sieve sieve
No. of ...
76
Purchased equipment cost of reactor found as followed;
Table3 Purchased equipment cost of reactor from CAPCOST
Vessels ...
77
For Drum 1 (V-103) For Drum 2 (V-104)
By taking length/diameter ratio as 3 from heuristics, founded diameter and height...
78
VESSELS
In our plant we need equipment for storage. Vessels are used to meet this need. For the feed
part, if there is ...
79
DME Storage Vessel
DME produced per day is calculated from material balance and found as,
Volumetric flow rate of metha...
80
Vessels Orientation Length/Height
(meters)
Diameter
(meters)
MOC Pressure
(barg)
Purchased
Equipment
Cost
V-101 Vertica...
81
Table6 Utilities Cost Data
Steam
High Pressure (40 bar g, sat) 16.50 $/mt
Medium Pressure (10 bar g, sat) 14.00 $/mt
Lo...
82
ECONOMIC ANALYSIS
All the equipment costs are added for the total equipment cost (based on the equipment cost
list),
To...
83
Thus, manufacturing capital is calculated by summing up fixed capital and working capital as
given below :
MC=17,289,47...
84
Payroll charges
It will be 35% of Labors and Supervision factor.
Payroll ch= (380160+192000) *0.35=200256 $/year
Repair...
85
ROI=27%
12.8. Polymath program needed for calculation of catalyst weight and reactor outlet temperature.
d(X)/d(W) = (-...
86
87
88
8.2. ChemCad Report for the Heat Exchangers
CHEMCAD 6.3.1
Simulation: First Heat Exchanger Date: 12/16/2013
Time: 18:21...
89
CHEMCAD 6.3.1 Page 1
Simulation: Full_Scheme_DME_Simulation Date: 05/21/2014 Time: 15:45:17
STREAM PROPERTIES
Stream No. 1...
Molar flow kmol/h 281.4525 281.4525 281.4519 169.5254
Mass flow kg/h 8985.1900 8985.1900 8985.1608 3835.7481
Temp C 340.96...
Std. sp gr. wtr = 1 0.673 0.801 0.998 0.801
Std. sp gr. air = 1 1.589 1.102 0.625 1.103
Degree API 78.6722 45.1014 10.3527...
- - Vapor only - -
Molar flow kmol/h 83.5497
Mass flow kg/h 3651.7291
Average mol wt 43.7073
Actual dens kg/m3 16.7073
Act...
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DME Plant project (Final Report)

DME Plant project (Final Report)

  1. 1. MIDDLE EAST TECHNICAL UNIVERSITY CHEMICAL ENGINEERING DEPARTMENT ChE 418 CHEMICAL ENGINEERING DESIGN I FINAL REPORT SUBMITTED BY: GROUP I Yousef Alsharif lkin Aliyev Kanan Atakışıyev Fariyaz Rustamov SUBMITTED TO: Prof.Dr.HAYRETTİN YÜCEL Assist. MERVE ÇINAR AKKUŞ DATE OF SUBMISSION: 21.05.2014
  2. 2. TABLE OF CONTENTS Abstract Table of Contents List of Tables List of Figures Nomenclature 1. Introduction 1 2. Design Basis 3 3. Process Flow Diagram 4 4. Process Description 5 5. Pipeline Design 6 6. Plant Layout 13 7. Equipment Design 14 8. Economic Evaluation 24 9. Discussion 28 10. Conclusion 32 11. References 33 12. Appendices 34 12.1. Physical and Chemical Properties 34 12.2. Equilibrium restriction for DME synthesis 35 12.3. Safety Considerations 36 12.4. Sustainability Considerations 41 12.5. Material and Energy Balance Calculations 43 12.6. Equipment Design for reactor 50 12.7. Cost Calculations and Equipment Cost Data 75
  3. 3. Abstract In this report, design of a dimethyl ether production plant is done by considering, raw materials to use, equipment specifications, utilities needed, economic analysis and safety issues. It is supposed to provide the plant with 60000 metric tons of methanol as a feed. Methanol dehydration reaction is known to be a catalytic reaction so a packed bed reactor with aluminum silicate as a catalyst is used. The process starts by pre-heating the methanol feed up to the boiling point then re-heat up to 250 0 C and sent to the reactor. The feed is given as liquid methanol with 99.5% wt. methanol. Since the methanol dehydration reaction is an exothermic reaction, the temperature in the reactor increases up to 365.5 0 C approximately to give 80% conversion. Finally the exit stream of the reactor is sent to separation towers in order to get the desired product (DME) with 99.7 % wt. Feed preparation for the DME separation column is handled at temperature of 90.7 0C and pressure of 10.4 bars by using condenser with a heat duty of 10274.8 MJ/hr. Amount of feed to the DME separation column is 282 kmol/hr. In DME separation column, 99.6 mole percent of DME is achieved in a top product stream. In order to have such a high purified product, 8 trays and a reboiler are used with an efficiency of 39%. Number of trays is found 7 by ChemCad simulation that confirms the result. Tray spacing is calculated as 0.762 m by using data from ChemCad simulation. In methanol separation column 99.5 mole percent of methanol is achieved in a top product stream that is sent through a recycle stream as a feed to the reactor. In order to have such a high purified methanol, 27 trays and a reboiler are used with an efficiency of 91.5%. Also, methanol separation column is simulated by using ChemCad that gave the same number of trays as a result. Also, tray spacing is calculated as 0.6 m by using data from ChemCad simulation and finally the height of the column was determined as 18.9 m. Economic evaluation analysis for the preliminary DME production plant design is carried out to estimate the feasibility of the plant. At the very beginning of this analysis, total fixed capital and working capital investments are estimated as 5,460,980 and 17,289,470$ respectively that gives a total manufacturing capital of 22,750,450$. Then the total manufacturing cost is estimated as 30,807,022$. Throughout these economic analyses the percentage net return on investment is estimated as 27%, 21.6% and16.2% for 100%, 80% and 60% production capacities respectively. Finally the rate on investment (ROI) is found as 27%.
  4. 4. List of Tables Table 2.1: Design basis for the dimethyl ether production Table 7.1. Equipment Schedule Sheet Table 8.1: Manufacturing Capital Table 8.2: Non-Manufacturing Capital Investment Table 8.3: Manufacturıng Cost Sheet Table 8.4: Estimate Of Annual Earnings & Return Table 12.1.1: Reaction conditions for DME synthesis Table 12.1.2: Physical properties of DME Table 12.5.1: Composition of feed and product Table 12.5.2.1: Amount of each species in each stream Table 12.5.2.3: Explanation of symbols that used in diagram Table 12.5.2.4: Molar flow rates of each stream Table 12.6.1: Parameters and its values Table 12.6.2: Description of the first heat exchanger streams and their temperatures Table 12.6.3: Description of the second heat exchanger streams and their temperatures
  5. 5. List of Figures Figure 1.1: Methods of production Figure 3.1: Flow diagram of DME production. Figure 12.2.1 Stoichiometric equilibrium conversion of DME and methanol synthesis Figure 12.5.1: Input- output diagram of the plant Figure 12.5.2.2: Diagram of the reactor Figure 12.5.2.3: Flow diagram of feed preparation Figure 12.6.1: CHEMCAD simulation for the feed preparation. Figure 12.6.2: Schematic draw of the first heat exchanger Figure 12.6.3: Schematic draw of the second heat exchanger Figure 12.6.4 : Block diagram for the DME Tower Figure 12.6.5.Gillilan correlation (1968 , McGraw-Hill) Figure 12.6.6 : Block diagram for the DME Tower
  6. 6. i NOMENCLATURE Symbols Definition Area Concentration of Species i Heat Capacity Diameter Nominal Inside Diameter Overall Column Efficiency Correction factor Molar flow rate of species i Liquid-Vapor Flow Factor Height Heat of Vaporization Heat of Reaction Specific Reaction Rate Length ̇ Mass Flow Rate Moleculer Weight of Species i Number of Stages ̇ Molar Flow Rate Pressure q Feed condition (liquid ratio) Heat Duty ̇ Volumetric Flow Rate Ideal Gas Constant R Reflux Ratio Rmin Minimum Reflux Ratio Rate of Reaction Residence Time Temperature Temperature Difference Log-mean Temperature Overall Heat Transfer Coefficient
  7. 7. ii Volume Catalyst Weight Drive Power Shaft Power Conversion Greek Symbols α Relative Volatility Viscosity Liquid Density Vapor Density Flooding Velocity Overall Efficiency Drive Efficiency Shaft Efficiency
  8. 8. 1 1. INTRODUCTION The production of high purity DME became one of the most important issues of the world industry in recent years. The reason of increasing demand to DME is its potential as a clean fuel for diesel engines due to its higher combustion quality, lower concentration of particulates and mono-nitrogen oxides in emission, low engine noise, high fuel economy and high efficiency [6]. There are two main methods of DME production; an indirect synthetic method using the dehydration reaction of methanol, and a direct synthetic method from natural gas, coal bed methane and synthetic gas made from coal, biomass and so on as shown in Figure1.1. Figure 1.1 Although, both methods are available, indirect synthetic method is preferred more widely due to its simple process and relatively low startup cost. Methanol dehydration reaction shown below is used in this process. 2 CH3OH CH3-O-CH3 + H2O
  9. 9. 2 In order to perform this reaction aluminum silicate catalyst is used. Between 250- 400 ˚C it is suitable for reaction in terms of catalyst activity temperature and side reactions. Conditions in the reactor must provide these conditions. It is an exothermic reaction which results in increase of temperature in adiabatic tubular catalyst reactor. In order to design process for indirect method of dimethyl ether (DME) production from methanol, certain steps should be considered. Generally process design should be started with the determination of design basis and then encompass desired production rate, product composition are decided. Overall material and energy balances are performed by referring pre- determined design basis information. Overall process could be briefly generalized by four steps; feed preparation, reactor, DME separation and methanol separation. In the first part, aim is to bring the inlet stream of reactor to the desired conditions in terms of temperature, pressure and phase of reactants by using a tank, pumps and heat exchangers. In the reactor, reaction takes place and the desired conversion should be achieved. After the reactor distillation columns are used to obtain desired product.
  10. 10. 3 2. DESIGN BASIS Table 2.1: Design basis for the dimethyl ether production Feed: Methanol Purity (wt %) – (rest is water) 99.5 Product: Dimethyl ether Purity ,wt % – balance is methanol 99.7 Capacity of the plant Methanol feed rate, mt/year 60 000 Stream time, h/year 8320 Utilities Available Steam High Pressure Steam (sat), bar g. 40 Medium Pressure Steam (sat), bar g. 10 Low Pressure Steam (sat), bar g. 5 Cooling Water Available Cooling Water Tower – max. values 4 bar, 25 ˚C CW Return – max. Values 1.8 bar, 40 ˚C Fuel Natural gas Electricity All voltages and phases are suitable for electric drives. Materials Handling Methanol Delivered by pipe to battery limits and stored Dimethyl ether Stores
  11. 11. 4 3. PROCESS FLOW DIAGRAM OF DIMETHYL ETHER PRODUCTION BY METHANOL DEHYDRATION Figure 3.1: Flow diagram of DME production. Process flow diagram given in Figure 2.1 displays DME production, feed preparation with preheater and heat exchanger for the reactor and two separation towers which are simulated with ChemCad v6.3.1. For the sake of simplicity the reboiler and condenser are embedded in to towers.
  12. 12. 5 4. PROCESS DESCRIPTION Plant that is considered to be designed, has a capacity to use 60,000 metric tons of DME as a feed per year. Production method is catalytic dehydration of methanol over an acid zeolite catalyst. A packed bed reactor (R-201) which is filled with solid catalyst particles is used to produce dimethyl ether. Fresh methanol, Stream 1, is combined with recycled reactant, Stream 13, and pre-heated by the first heat exchanger (E-201).Then this mixture is vaporized by the second heat exchanger, E-202, prior to being sent to a fixed-bed reactor (R-201) operating between 250°C and 370°C. The stream leaving reactor, Stream 7, is then cooled (E-203) prior to being sent to the first of two distillation columns: T- 201 and T-202. DME product is taken overhead from the first column (Stream 10). The second column separates the water from the unused methanol. The methanol, Stream 13, is recycled back to the front end of the process, and the water is sent to wastewater treatment to remove trace amounts of organic compounds.
  13. 13. 6 5. PIPELINE DESIGN In order to find the optimum pipe diameter following equations were used. For turbulent flow in steel pipes, (NR>2100)  Di ≥ 1 in Di,opt = 3.9 (qf 0.49 )*( ρ0.13 )  Di < 1 in Di,opt = 4.7 (qf 0.49 )*( ρ0.14 ) For viscous flow in steel pipes, (NR <2100)  Di ≥ 1 in Di,opt = 3.0 (qf 0.36 ) * (μ0.18 )  Di < 1 in Di,opt = 3.6 (qf 0.4 ) * (μ0.2 )
  14. 14. 7 ρ = fluid density b/ft3 qf = fluid flow rate ft3/s μ = fluid viscosity lb/ft.s Pipeline for Stream: 1 Assume that pipe diameter is greater than 1 in and turbulent flow. 49 =317 = = 0.000363 = 2.17 in =0.2144 = = 5273 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream 2: Assume that pipe diameter is greater than 1 in and turbulent flow. 49.343 =317.875 = = 0.00036 = =0.2145 = = 5266 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream : 3 Assume that pipe diameter is greater than 1 in and turbulent flow. 43.52 =396 = = 0.00016 =
  15. 15. 8 = = = 12078>>> 2100 Nominal size of pipe, in =1/8 Schedule no= 80 , Wall thickness, in = 0.095 Pipeline for stream:4 Assume that pipe diameter is greater than 1 in and turbulent flow. 0.736 =396 = = 1.18*10^-5 =1.388 = = = 4732 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream : 5 Assume that pipe diameter is greater than 1 in and turbulent flow. 0.5549 =421 = = 1.36*10^-5 = 1.375in =0.708 = = 3314 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream : 6 Assume that pipe diameter is greater than 1 in and turbulent flow. 0.651 =421 = = 1.19*10^-5 =1.404 in
  16. 16. 9 = = = 4354 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068
  17. 17. 10 Pipeline for Stream : 7 Assume that pipe diameter is greater than 1 in and laminar flow. 3.75 =421 = = 0.000139 = = 0.431 = = 1709 <<< 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream : 8 Assume that pipe diameter is greater than 1 in and turbulent flow. 47.35 =151 = = 0.00012 =1.546 in =0.2012 = = 10199 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 80 , Wall thickness, in = 0.095 Pipeline for Stream : 9 Assume that pipe diameter is greater than 1 in and laminar flow. 1.31 =270 = = 7.03*10^-5 = 1.26 in = 0.541
  18. 18. 11 = = 1063 <<< 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream : 10 Assume that pipe diameter is greater than 1 in and turbulent flow. 0.98 =396 = = 9.72*10^-6 = = = = 7377 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 80 , Wall thickness, in = 0.095
  19. 19. 12 Pipeline for Stream : 11 Assume that pipe diameter is greater than 1 in and turbulent flow. 55 =73 = = 9.92*10^-5 = 1.136in = =0.1799 = = 9457 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 80 , Wall thickness, in = 0.095 Pipeline for Stream : 12 Assume that pipe diameter is greater than 1 in and turbulent flow. 0.677 =78 = = 9.28*10^-6 = 0.66in = 0.568 = = 2286 >>> 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068 Pipeline for Stream : 13 Assume that pipe diameter is greater than 1 in and laminar flow. 2.48 = 421 = = 0.000158 = 1.67in = 0.48 = = 1048 <<< 2100 Nominal size of pipe, in =1/8 Schedule no= 40 , Wall thickness, in = 0.068
  20. 20. 13 6. Layout (Plot Plan)
  21. 21. 14 7.1. EQUIPMENT SCHEDULE Table 7.1. Equipment Schedule Sheet Item No. No. of Required Equipment Name Size(Each) V-101 3 Methanol Storage Tank 73.01 m3 V-102 1 Methanol Feed Drum 7.64 m3 V-103 1 DME Reflux Drum 2.15 m3 V-104 5 DME Storage Tank 61.15 m3 V-105 1 Methanol Reflux Drum 0.72 m3 P-101A/B 2 Methanol Feed Pump 9.48 kw P-102 A/B 2 DME Tower Pump 2.16 kw P-103 A/B 2 Methanol Tower Pump 8.10 kw R-101 1 Reactor 4.8 m3 E-101 1 Reactor Preparation Preheater 85 m2 E-102 1 Reactor Preparation Heater 153.2 m2 E-103 1 Separator Feed Prep. Condenser 26.3 m2 E-104 1 DME Tower Condenser 122 m2 E-105 1 DME Tower Reboiler 30.16 m2 E-106 1 Methanol Tower Condenser 12.68 m2 E-107 1 Methanol Tower Reboiler 14.88 m2 E-108 1 Waste Water Cooler 43.6 m2 T-109 1 DME Distillation Tower 8.36 m3 T-110 1 Methanol Distillation Tower 25.26 m3
  22. 22. 15 SIEVE TRAY COLUMN SPECIFICATION SHEET Page 1 of 3 Item No. : T-101 By : Group I Name : DME Separation Column Date: 20-03-2014 Number Required : Function: DME Purification Material Balance: Feed Overhead Bottoms Reflux Reboiler Vapor Phase, % vapor 30% vapor Vapor (100%) Liquid (0%) kg/h mol/h 281000 112000 169500 Mean MW. Operating Conditions: Top Feed Plate Bottom Temperature, °C 47.7 90.7 152 Pressure, bar 10.4 10.4 10.4 Reflux & Stage Calculation: Method of Calculation Gilliland correlation (Wankat,2011) Minimum equilibrium stages (inc. reboiler) Minimum reflux ratiol (L/D) 0.202 Operating reflux ratio 0.755 Feed, % vapor 30% vapor Req'd equilibrium stages at oper. reflux (inc. reboiler ) 7 stages (chemcad simulation) Above feed 4 Below feed 3 Total 7 stages
  23. 23. 16 Est. Overall plate efficiency, % 0.39 Calculated plates 9 stages Page 2 of 2 Column Design: Materials of construction Column Shell Trays Internal diameter, cm 61 Normal tray spacing, cm 61 Feed tray numbers: Normal 4 Optional 4 Column height (N-1) tray spacings (9-1)*0.61m=4.88 m Disengagement space above top plate, m Extra space at feed trays Normal sump height Disengagement space above sump Skirt height Total column height,m Vessel design temp., °C Vessel design press., barg. Wall thickness, cm Includes corrosion allow., cm Insulation required (Yes or No) Tray Design: Trav type
  24. 24. 17 Tower ID to fit, m Total tower cross-section area, m 2 Normal tray spacing, m Number liquid passes Perforations : Hole diameter, cm Total hole area per tray, m 2 Overflow weir height, cm Downcomer apron clearance, cm Downcomer location (Side or Center) Side downcomer each Center downcomer total Overflow weir lengths, cm Side downcomer each Center downcomer each Areas, m 2 Downcomer, each pass Downcomer, total Downcomer, % of tower Net tower area Tray active area Hole area/active area Weir length/tower diameter (for side downcomer) Downcomer width/tower diameter Page 3 of 3 Tray Dynamics Calculations : Top Tray Bottom Tray Pressure, bar g. Temperature, ºC Loading: Vapor load, kg/hr
  25. 25. 18 m 3 /h Liquid Ioad, kg/h m 3 /h L/V ratio, kg/kg Properties : Vapor density, kg/m 3 Liquid density, kg/m 3 Liquid surface tens., N/m Liquid visc., cp. Load Factors L V W W LV V L F    Kl, chart (σ = 20 ) Kı, flood (with σ = ) Pressure drop: Per tray, cm liquid barg. Total, for column, cm liquid Flooding criteria: Actual Uf, cm/s Flood Uf, cm/s % vapor flooding Entrainment ratio (liquid): ψ= kg entrain/kg downflow Weep point: Weep Uf, cm/s Actual Uf, cm/s Weep Uf, % actual Mise. dynamic factors Liquid crest over weir, cm Liquid gradient Mean height of froth, cm
  26. 26. 19 Downcomer capacity: Height clear liquid in downcomer,cm Height froth (Assume Φ=0.5), cm % downcomer floor Downcomer residence time, s (min.=3 sec) Ratio, min./actual res.time SIEVE TRAY COLUMN SPECIFICATION SHEET Page 1 of 3 Item No. : T-102 By : Group I Name : Methanol Separation Column Date: 20-03-2014 Number Required : Function: Methanol Recycling Material Balance: Feed Overhead Bottoms Reflux Reboiler Vapor Phase, % vapor Liquid (0%vapor) Vapor (100%) Liquid (0%) kg/h mol/h 169500 55000 114500 Mean MW. Operating Conditions: Top Feed Plate Bottom Temperature, °C 152 139 181 Pressure, bar 10.4 10.4 10.4 Reflux & Stage Calculation: Method of Calculation McCabe-Thiele method Minimum equilibrium stages (inc. reboiler) Minimum reflux ratiol (L/D) 1.251
  27. 27. 20 Operating reflux ratio 1.251 Feed, % vapor Liquid (0% vapor) Req'd equilibrium stages at oper. reflux (inc. reboiler ) 28 stages Above feed 23 Below feed 5 Total 28 Est. Overall plate efficiency, % 91.5 Calculated plates 27 + reboiler Page 2 of 2 Column Design: Materials of construction Column Shell Trays Internal diameter, cm 61 Normal tray spacing, cm 61 Feed tray numbers: Normal 23 Optional 23 Column height (N-1) tray spacings (28-1)*0.61m= 16.47m Disengagement space above top plate, m Extra space at feed trays Normal sump height Disengagement space above sump Skirt height Total column height,m Vessel design temp., °C
  28. 28. 21 Vessel design press., barg. Wall thickness, cm Includes corrosion allow., cm Insulation required (Yes or No) Tray Design: Trav type Tower ID to fit, m Total tower cross-section area, m 2 Normal tray spacing, m Number liquid passes Perforations : Hole diameter, cm Total hole area per tray, m 2 Overflow weir height, cm Downcomer apron clearance, cm Downcomer location (Side or Center) Side downcomer each Center downcomer total Overflow weir lengths, cm Side downcomer each Center downcomer each Areas, m 2 Downcomer, each pass Downcomer, total Downcomer, % of tower Net tower area Tray active area Hole area/active area Weir length/tower diameter (for side downcomer) Downcomer width/tower diameter
  29. 29. 22 Page 3 of 3 Tray Dynamics Calculations : Top Tray Bottom Tray Pressure, bar g. Temperature, ºC Loading: Vapor load, kg/hr m 3 /h Liquid Ioad, kg/h m 3 /h L/V ratio, kg/kg Properties : Vapor density, kg/m 3 Liquid density, kg/m 3 Liquid surface tens., N/m Liquid visc., cp. Load Factors L V W W LV V L F    Kl, chart (σ = 20 ) Kı, flood (with σ = ) Pressure drop: Per tray, cm liquid barg. Total, for column, cm liquid Flooding criteria: Actual Uf, cm/s Flood Uf, cm/s % vapor flooding Entrainment ratio (liquid): ψ= kg entrain/kg downflow Weep point: Weep Uf, cm/s
  30. 30. 23 Actual Uf, cm/s Weep Uf, % actual Mise. dynamic factors Liquid crest over weir, cm Liquid gradient Mean height of froth, cm Downcomer capacity: Height clear liquid in downcomer,cm Height froth (Assume Φ=0.5), cm % downcomer floor Downcomer residence time, s (min.=3 sec) Ratio, min./actual res.time
  31. 31. 24 8. Economic Evaluation  Estimate Of Capital Requirements Table 8.1: Manufacturing Capital I. Manufacturing Capital Item No. Equipment Name No. Req´d. Total Cost ($) V-101 METHANOL STORAGE TANK 3 435000 V-102 DME REFLUX DRUM 1 9130 V-103 METHANOL REFLUX DRUM 1 4920 V-104 DME STORAGE TANK 3 375000 E-101 REACTOR PREPERATION PREHEATER 1 22303 E-102 REACTOR PREPERATION HEATER 1 27700 E-103 SEPERATOR FEED PREPERATION CONDENSER 1 16745 E-104 DME TOWER CONDENSER 1 25300 E-105 DME TOWER REBOILER 1 15300 E-106 METHANOL TOWER CONDENSER 1 15500 E-107 METHANOL TOWER REBOILER 1 15600 E-108 WASTE WATER COOLER 1 18500 P-201 FEED PUMP 1 17946 P-202 DME REFLUX PUMP 1 2564 P-203 METHANOL REFLUX PUMP 1 3462 T-101 DME TOWER 1 10700 T-102 METHANOL TOWER 1 35000 R-201 REACTOR 1 7376 Total Process Equipment 1058046 Total Mfg. Capital Based on Lang Factor = 4 4232184 Contingency at 10% 423218
  32. 32. 25 Table 8.2: Non-Manufacturing Capital Investment II. Non-Manufacturing Capital Investment Total Cost ($) Proportionate share existing capital estimated at 25 % mfg. cap. 1058046 III. Total Fixed Capital Investment Sum of I & II 5460980 IV. Working Capital Raw Material Inventory 13826504 Goods in Process (included in utilities) Finished Product Inventory 42865000 Stores Supplies 12696 All other Items 4286500 Total Working Capital 17289470 V. Total Fixed & Working Capital Investment Sum of III & IV 22750450
  33. 33. 26 Table 8.3: Manufacturıng Cost Sheet Manufacturıng Cost Sheet LOCATION: İZMİT Design: DME Plant per Yr. (8320 h) Mfg. Capital: 3222313 $ RAW MATERIALS UNIT QUANTIT Y $/UNIT $/YEAR $/kgDME Methanol mt 60000 220 13200000 0.3081 Catalyst mt 3.12 18000 56160 0.00131 GROSS R.M. COST 13256160 0.3094 NET MATERIAL COST 56160 0.0013 DIRECT EXPENSE UNIT QUANTIT Y $/UNIT $/YEAR $/kg Steam (mps) Steam (hps) Steam (lps) Mt Mt Mt 61243.5 37681.3 1141728.6 14 16.5 12.5 857409 621742 14271608 0.020 0.146 0.334 Electricity kWh 164236.8 0.11 18066.05 0.0003 Cooling Water 1000 m3 1558.9 15 23384 0.00055 TOTAL UTILITIES 15792209 0.5 Labor 380160 0.0063 Supervision 192000 0.0032 Payroll Charges (35%Labor and supervision) 200256 0.0033 Repairs (6% of Mfg. Cap/year) 253931 0.0059 Product Control Factory supplies Laboratory (2% of Mfg. Cap/year) 84643 0.0019
  34. 34. 27 Technical service Royalty Depreciation ( 8% of Mfg. Cap/year) 338574 0.0079 Factory Indirect Expense ( 4% of Mfg. Cap/year) 169287 0.0039 TOTAL MANUFACTURING COST 0.721 Table 8.4: Estımate Of Annual Earnings & Return Estımate Of Annual Earnings & Return Production at % of Capacity 60% 80% 100% I. Gross Sales Annual Production Rate, ton/yr 25719 34292 42865 DME Sales Price, $/mt 1000 1000 1000 Gross Sales Income 25719 34292000 42865000 II. Less Manufacturing Cost Manufacturing Cost 18484213 24645618 Gross Profit 7234787 9646382 III. Less SARE Sare Expenses at 10% Sales 2571900 3429200 Net Income Before Income Taxes 4662887 6217182 7771478 IV. Less Income Taxes Income Taxes at 20% Net Income 932577 1243436 1554295 Net Annual Earning 3730310 4973746 6217183 V. Return on Total Investment Total Fixed & Working Capital 13650270 18200360 22,750,450 % Net Return on Investment 16.2% 21.6% 27 %
  35. 35. 28 9. Discussion The objective of this study is to make preliminary design for a plant which produces DME by using 60,000,000 kg /year methyl alcohol with 99.5 % purity, used as start point for material balance in the process.and with a stream time of 8320 h/year. In order to achieve this aim, one reactor, two distillation towers with condensers and reboilers, four heat exchangers, three pumps, 2 drums, 6 storage tanks are designed. While equipment necessary for the process is designed, material and energy balance, design heuristics and Chemcad simulation are used. Indirect method, that is, dehydration of methanol is used in this plant to produce DME. Methanol needed for the process is bought as raw material whose purity is 99.5 %wt. Silica alumina is used as catalysis in this process. The aim is defined as DME production with purity of 99.7 %wt . Natural gas is used as fuel. To begin with, horizontal arrangement is preferred for streams in liquid phase. While energy balance is performed around the drum, heat of mixing is neglected due to the fact that it is expected to be low compared to the flow enthalpies. Secondly, pumps are designed according to heuristic to be able to calculate power consumed both for shaft and driver work. While pumps are designed efficiency is determined by considering volumetric flow rate and pressure difference around pump according to flow diagram is used in calculation. For pump, shaft work is found as 8.17 kW and efficiency is found as 0.45. Spare must be considered for all three pumps so two pumps are provided for each pumping purpose. While reactor is being designed, expected conversion which is 0.8 is considered at first. According to conversion and needed production rate, material balance around reactor is performed. In addition, energy balance around reactor is conducted and it is assumed that reactor is adiabatic. Temperature calculation gives us outlet temperature of reactor as 365.5 0 C. Since the chosen catalyst is deactivating above 4000 C, calculated outlet temperature is considered to be in appropriate range. In addition, it is a significant point that in working temperature range silica alumina is active. While performing material balance feed is assumed as pure methanol. It is a reasonable assumption since water entering reactor is negligible with respect to methanol. Furthermore, in the recycle stream only methanol exists. Considering volume value of different types of reactor packed bed reactor is more advantageous to use in this process.
  36. 36. 29 Silica alumina is an effective catalyst for dehydration reaction of methanol so it is chosen as catalyst. Weight of catalyst is calculated as 3350 kg. Reactor volume is estimated as 4.8 m3 . In this calculated volume, expected conversion which is about 0.8 can be achieved.By using calculated volume and cross sectional area values, length of reactor can also be found. Furthermore, thickness of the reactor is calculated as 1.04 cm and construction material of reactor is chosen as carbon steel. Working pressure of reactor and maximum allowable stress of the material are considered while determining the thickness and material of the reactor. In order to make feed ready to enter the reactor, it must be heated since methanol is stored at 45C. To achieve this aim, a preheater is designed whose function is to heat methanol from 45 C to 154 C. Steam is preferred as heating medium. After that, another heat exchanger is designed to rise the temperature of methanol from 154 C to 250 C where reactor effluent is used as heating medium, so that, steam does not needed for this heat exchanger. As a result, it can be mentioned as beneficial for economic aspect. At the e it of this heat exchanger, reactor effluent is obtained at 260 C. Therefore, cooling of reactor effluent to 100 C for the entrance of separation unit is also made easier and less cooling water is required than it would be if no heat integration is used. Cooling water is available at 25 C so cooling medium is fed to exchanger at 25 C. Maximum allowable temperature to which cooling water can be reached is 40 C so e it temperature of cooling medium is fixed at 40 C. In addition, another heat exchanger is needed to cool waste water for environmental aspects. While heat transfer area calculations are conducted, overall heat transfer coefficients are determined with respect to nature of process. In order to obtain DME as a product from rector effluent, DME separation tower is designed. In addition, separation of methanol from water methanol mixture is necessary to recycle methanol to reactor. Hence, methanol separation tower is designed. Sieve trays are used for economic purposes. Furthermore, R/Rmin is chosen as 1.3 by taking into consideration design heuristics and economic aspects. In addition for both columns flooding and weeping are checked and it is seen that there is no such a risk. First of all, DME-Methanol tower is designed by using Chemcad simulation program. Because there are three components in the first column, hand calculation is difficult to conduct. At first short cut method is used and then some information is derived from that simulation. SCDS simulation method is used with the help of short cut column simulation results. Chemcad simulation gives ideal number of
  37. 37. 30 stages as 7 and bu hand calculation is found 9. In order to obtain actual number of stage overall efficiency is calculated by using Gilliland correlation. Overall efficiency and actual number of stages are found as 42.8 % and 21 respectively. Moreover, minimum number of stages and feed point location are determined by hand calculation for first column. The results are found as 5 and 4 stages respectively which are close to each other. Feed enters the tower from the middle of the tower. Secondly, methanol and water mixture which is bottom product of first column is fed to the second tower. For this column both hand calculation that is, Mc- Cabe-Thiele method, design heuristics, sizing equations and Chemcad simulation are done. It is neglected that there is a trace amount of DME in the feed of second column. Ideal number of stages is calculated by using McCabe-Thiele method. Mc-Cabe-Thiele method involves its own assumptions which are molal over flow, negligible heat loss and it states that for a mole of vapor which condenses there is a mole of liquid which vaporize. Mc-Cabe-Thiele method gives 28 ideal numbers of stages which is consistent with Chemcad result. Overall efficiency and actual number of stages are found as 90.3 and 31 respectively. Heuristic revealed at reference list for column design are used to compute total column height and diameter. It is seen that both tower height and tower height / diameter ratio are within the safe zone and satisfy design parameter. Column diameter is calculated by hand as 0.76 m. Economic analysis is crucial since it is the main factor to determine the success of a project. Economic analysis reveals the amount of profit under operating condition of a plant. Both capital investment cost and production cost must be examined for a successful economic analysis. While economic analysis is being conducted, 2012 September CEPCI values were used to calculate purchasing cost of the equipment used in DME production plant. Chemcad program was used to calculate estimate cost of pumps and CapCost software was used for all other equipment. It is necessary to specify properties of equipment such as volumes, heat transfer areas, diameters and construction materials to be able to use this program. Moreover, Lang factor method was used for total manufacturing capital. When working capital is considered the main aim was to decrease it as much as possible. To satisfy this aim just in time operation and good planning were provided to the DME production plant. The important function of just in time operation is to get rid of wasteful activities which increases the working capital but does not contribute the value of the product. Hence, raw material inventory and working process inventory were ignored while working capital calculation was done. In
  38. 38. 31 addition, heat integration is applied by using reactor effluent to heat feed in the process to decrease cost of utility. It is effect can be seen by the help of net present value method. If heat integration was not applied, net present value would be lower. Construction material of equipment is selected as carbon steel. It is stated that “Stainless steel and carbon steel are typically used in methanol plants.” [6]]. However, for long term operations stainless steel is a better construction material. DME production preliminary design is analyzed economically according to the net income and rate of return on investment results in order to ensure the feasibility of the design. The total manufacturing capital is approximately estimated as 22750450$ that is the summation of total fixed capital and working capital investments while total manufacturing cost is estimated as 30,807,022$. The net annual profit is estimated as for 100% capacity working plant. However, as it is known that in real industries it is impossible to operate a plant with 100% capacity. Therefore, the rate of return on investment for 60% and 80% are estimated as 16.2% and 21.6% respectively. Regarding all the calculations required for the economic analysis done in result’s part, it may be concluded that producing DME from methanol is quite feasible.
  39. 39. 32 10. Conclusion The aim of the project is to make preliminary design for DME production including economic analysis. One reactor, two distillation towers with condensers and reboilers, four heat exchangers, three pumps, two drums and six storage tanks are designed and pipeline is constructed according to heuristics and main results are summarized in specification sheets. Either material or energy balance is performed for each equipment. Reactor is designed as a packed bed reactor to carry out dehydration reaction of methanol. Two of heat exchangers are available to prepare feed before the entrance of reactor. One of the heat exchangers prepares the reactor effluent for the feed of separation unit. The function of other exchanger is cooling waste water which appears at the exit of separation tower. Two pumps are placed to continue the flow of liquids at desired pressure to separation towers from drums and one of the pumps is placed in order to send methanol to feed preheater from methanol storage tank. Storage tanks are constructed in the process so as to make certain amount of feed and product available at any time. Drums exist at the exit of condensers of both separation towers to keep reflux for a certain time. Pipeline is built between all equipment to convey materials in a safe way during process. Hence, DME is obtained with purity of 99.7 wt%. The designed plant aims to use 60,000 metric tons of Methanol, with 99.5 % purity, as a feed per year and having stream time of 8320 h/year. Finally, economic analysis was performed in order to confirm the feasibility for DME production preliminary plant design. Total fixed capital investment, working capital investment, total manufacturing capital and total manufacturing cost were estimated accordingly. Then, the net annual profit was approximately estimated as 6,217,183$/year with 27% return on investment when 100% capacity (full) is considered. However, in real life it is impossible to perform with such capacity. Therefore, rates of return on investment for 60% and 80% are estimated as 21.6% and 16.2% respectively. To conclude, it is reasonable to move a detailed design since preliminary design has given acceptable return on investment, according to interest rate in Turkey.
  40. 40. 33 11. References [1] Timmerhaus, K. D., Peters, M. S. & West R. E. (2003). Plant Design and Economics for Chemical Engineers, 5th ed. New York: McGraw-Hill. [2] Sinnot, R.&Towler G.(2009). Chemical Engineering Design, 5th ed. Oxford: Elsevier. [3] Turton, T., Bailie, R.C, Whiting, W.B. and Shaeiwitz, J.A.,(2009) Analysis, Synthesis and Economics of Chemical Processes, 3rd ed., New Jersey: Prentice Hall. [4] Dougles, J.M.., Conceptual Design of Chemical Processes, (1988) New York: McGraw Hill. [5] Seider, W.D.., Seader, J.D..,LewinD.R.(2004) Product and Process Design Principles,Synthesis, Analysis and Evaluation. 2nd ed. New York: John Wiley &Sons [6] Keith O., Trevor C., “Cetane Number in Diesel Fuel’ Automotive Fuels Reference Book, SAE ISBN 1-56091-589-7 (1995) evergreenamerika.com” [7] “Plant Design And Economics For Chemical Engineers”, Max S. Peters, Klaus D. Timmerhaus, Ronald West.,5th edition,2002 [8] Turton, R., Bailie, R. C., & et al, R. C. (2013). Analysis, synthesis, and design of chemical processes. (4th ed). Upper Saddle River, N.J.: Pearson Education, Inc. [9] “ME: Multi-Use, Multi-Source Low Carbon Fuel” nternational DME association, http://www.aboutdme.org/ (01.12.2012) [10] Retrieved from http://www.igu.org/html/wgc2006/pdf/paper/add10696.pdf
  41. 41. 34 12. Appendices 12.1 Physical and Chemical Properties of methanol and dimethyl ether  DME from synthesis gas (CO+H2) 2CH3OH→CH3OCH3+H2O (Methanol Dehydration Reaction) The required pressure for DME synthesis reaction and catalyst ratio (W/F) that is defined as the catalyst weight (kg) to the reactant gas flow rate (kg.mole/h) are shown in the below table, Table 12.1.1. Reaction conditions for DME synthesis  Physical properties of dimethyl ether. Table 12.1.2. Physical properties of DME Properties Dimethyl ether Chemical formula CH3OCH3 Boiling point (K) 247.9 Liquid density (K) 0.67 Specific gravity 1.59 Vapor pressure (atm) 6.1 Heat of vaporization (kJ/kg) 467 Igntion temperature ( K) 623 Cetane number 55 - 60 Net calorific value (106 J/kg) 28.9 Reaction condition Temperature ( 0 C )Pressure ( Mpa )Fed syn-gas(H2/CO) ratioW/F ((kg.h)/kg) Experimental 240 - 280 3.0 - 7.0 0.5 - 2.0 3.0 - 8.0 Standard 260 5 1 4
  42. 42. 35 12.2 Equilibrium restriction for DME synthesis Since it is known that methanol synthesis reaction is an equilibrium restricted reaction, in other words; the equilibrium conversion of synthesis gas (CO+H2) is strongly affected by pressure, temperature and stoichiometric ratio [H2/CO] as can be seen in the figure 1.2.1 Figure 12.2.1 Stoichiometric equilibrium conversion of DME and methanol synthesis
  43. 43. 36 12.3: SAFETY CONSIDERATIONS Safety is the control of recognized hazards to achieve an acceptable level of risk. It includes the inherent safety, hazards and operability analysis (HAZOP), material hazards and fire protection. This can take the form of being protected from the something that causes health or economical losses. The design process is based on the material, fire protection and explosion considering plant, unit layout, storage tanks, distillation towers, reactors and piping system. In order to process operation friendly and economic, process requirements, environmental regulations, location and process materials should be taken consideration. Furthermore, so as to provide good plant operating written instruction in the use of substances and the risk involves. [8]The adequate training of personnel should be provided about devices and plant operations. Protective clothing should be supported personnel. Also, housekeeping and personal hygiene should be checked regularly. Regular medical checkups on employees and chronic effects of materials should be considered. Preventative and total productive maintenance strategy should be applied to equipment. Moreover emergency trainings should be done regularly. Steam traps and security valves should be equipped especially when handling high pressure steam. [8] Another important consideration is shipping regulations of DME. The detailed information is given below. Shipping regulations Proper shipping name: Dimethyl ether Hazard class number: 2.1 (Flammable gas) UN identification number: UN 1033 Packing group: p 200
  44. 44. 37 Dot labels required: Flammable gas Marine pollutant: DME is not classified as a marine pollutant DME packages: Packages should be implemented in reusable/returnable pressure containers which have the following properties: o Steel cylinders (70 – 100 Ibs) o Tank trucks (30,000 – 35,000 Ibs) o Tank cars (100,000 + Ibs) Transport on vehicles where load space is not separated from the driver’s compartment should be avoided. Vehicle driver should be aware of the potential hazards of load and should know what to do in the event of an accident or an emergency. Before transporting DME containers should be firmly secure. Cylinder valve should be checked to be closed and not leaking. Valve protection device must be correctly fitted. Adequate ventilation must be provided. Applicable regulations should be complied [9]. Under the process hazard analysis requirement, it should be completed that one of the analysis techniques listed: o What if o Checklist
  45. 45. 38 o FMEA o FTA o HAZOP HAZOP is chosen for this design as the process hazard analysis method since it is the most widely used method in the chemical process industries.
  46. 46. 39 15.3. HAZOP STUDY Table 15.1. Hazop Study for Reactor Guide Word Deviation Cause Consequences Action No No flow -Blockage in line -No methanol in storage tank -Feed pipe rupture -Supply pipe rupture -Valve is closed -Pump is closed -Decrease in production rate until no production -Cleaning of lines -Level control system -Maintenance of pipes -Automatic valve -Automatic pump More of Higher flow at reactor entrance and feed -More amount of opening of valve -Low conversion in previous pass -Lower temperature in feed to the reactor -Explosion -Increase in quantity of methanol in recycle stream -Automatic valve -Check reactor conditions (Catalyst efficiency, temperature, pressure) Less of Less rate of flow at entrance and feed -Less amount of opening of valve -Low recovery of methanol in methanol tower -Low product rate -Higher temperature in feed to reactor -Automatic valve -Temperature control at reactor feed preparation
  47. 47. 40 As well as -Impurities in feed stream -Water in recycle system -Problems in raw material -Fouling in pipes -Low conversion rates -Decrease in quality of product -Impurities mix with feed stream to reactor -Quality control of raw material and product - Maintenance of pipes Part of -Higher methanol fraction -Less methanol fraction -High quality of feed -Less quality of feed -More pure DME production than intended -Less pure DME production than intended - Quality control of feed stream and product Reverse -Reverse of flow -No probable cause -Decrease in production rate until no production -Consider interlock in feed stream Other than -Liquid raw material replaced phase feed -Wrong connection during plant modification -Explosion -Better management of change procedure
  48. 48. 39 12.4: SUSTAINABILITY CONSIDERATIONS Sustainability is an important consideration for chemical plants and industry. Everything that we need for our survival and well-being depends, either directly or indirectly, on our natural environment. Sustainability creates and maintains the conditions under which humans and nature can exist in productive harmony, that permit fulfilling the social, economic and other requirements of present and future generations. Sustainability is important to making sure that we have and will continue to have, the water, materials, and resources to protect human health and our environment.[2] For these reasons, plants and companies are asked to report their pollution prevent activities with the waste management hierarchy with the steps which are: (from most to the least desirable) [10] 1. Source reduction 2. In-process recycle 3. On-site recycle 4. Off-site recycle 5. Waste treatment 6. Secure disposal 7. Release to environment There are some physical properties which has influence on environmental pollutions. They are melting point, boiling point, vapor pressure, Henry’s law constant, Octanol-water partition coefficient, water solubility, soil sorption coefficient, bio-concentration factor. [10] The most important issues while trying to reduce the impact on environment while designing chemical plant are to minimize generation of waste product from reactor, design separation systems for maximum recovery and minimum energy usage, minimize effluent streams containing waste, minimize leaks during the storage and transfer operations. [10] Unreacted raw materials need to be separated and recycled. It helps not to put extra chemicals to environment while it is reducing the cost. If they were not recycled, they will lead subsequent reaction, emission or combustion all of which are undesirable. [10] In the production of DME, there is a recycle from the reactor for unreacted materials.
  49. 49. 40 Heat integration is another important issue to be considered from the environmental point of view since heating and cooling operations release extra carbon dioxide to the environment. It is important since extra energy consumption is a disadvantage for both environment and economics. [10] Heat integration is done also for the process of DME. Another important issue is about the separation units. Since no perfect separation exists, there are always trace contaminants in any pure stream. The aim of pollution preventing is to minimize these trace contaminants. [10] In DME production, 2 separation column is used. In distillation extra trace contaminants do not exist. However, it requires heating and cooling both of which gives carbon dioxide to environment. Thus, distillation columns need to be designed such that they use minimum energy for heating and cooling. The heat integration of boilers and condensers are also done in DME production design. Another issue is the storage tanks which introduce the emission problem. If there are volatile liquids in storage tanks there will be a vapor which is in equilibrium with it liquid. When liquid is pumped through these tanks from the bottom, there will be an elevation of liquid. The vapor of volatile material needs to be collected and recycled to the tanker truck which provides liquid to the tank. The ventilation of vapor to the atmosphere is a wrong action the take. [10] There are storage tanks of methanol and DME as volatile liquid storages. Boiling points for methanol and DME are 337.6 and 247.9 in Kelvin, respectively. They are volatile liquids. Thus, the emission of them needs to be considered as explained above. Finally, there is a product of waste water inside DME production process. That waste water contains methanol since before it is collected there is a separation column. As it is stated before there is no perfect separation. Thus, that waste water from the second separation unit will contain trace amount of methanol in it. In the overall calculations it is neglected since it is a preliminary design. However, in real operations there will be trace amount of alcohol in it. It is wrong to release it to the environment directly. There needs to be a waste water treatment unit. After the waste water treatment that clean water can be used for other purposes in plant.
  50. 50. 41 12.5 : Material and Energy Balance Calculations OVERALL MATERIAL BALANCE 12.5.1 Input-Output Diagram of the Plant B A C Figure 12.5.1: Input- output diagram of the plant The symbols on the diagram show the total mass flow rate of feed, product and byproduct water. Compositions of these are given in table 4.1.1 and 4.1.2. Table 12.5.1 Composition of feed and product Feed- A Species Compositon Methanol 99.50% Water 0.50% Product -B Species Compositon Methanol 0.30% DME 99.70% OVERALL PROCESS Product Water Feed
  51. 51. 42 12.5.2 Overall Material Balances The calculations are made based on process design basis. Overall process is selected as a system and amount of methanol is selected as basis to make material balance calculations. System: Overall Process Basis: 60000 mt/year of methanol as feed (A) Overall material balance: A = B + C Material balance on specie A : ( ) ( ) ( ) Two equations and two unknowns (B & C) Using above equations for B and : → B = 43002 mt/year → C = 16998 mt/year Mass flow rates are converted from mt/year to kmol/h using stream time which is 8320h/year to be used in simulation of the overall process in ChemCad. Results are shown in table 4.2.1. Molecular weight of methanol is 32 ton/tmol and 46 ton/tmol for DME. Table 12.5.2.1: Amount of each species in each stream Feed Species Flow rate(kmol/h) Methanol 224.2 Water 2 Product Methanol 0.485 DME 112 Waste Water Water 113.2
  52. 52. 43 MATERIAL AND ENERGY BALANCES FOR REACTOR AND REACTOR FEED PREPARATION  Material Balance around Reactor To make this calculation, flow rates of entering and leaving species to the reactor must be known. It is assumed that amount of material that enters the process enters to the process and amount of material that leaves from process also leaves the reactor. However there is difference in the amounts because of the recycle of methanol. So, firstly recycle is calculated using the values in table 4.2.1. To do that, reactor is selected as a system and amount of recycle methanol is symbolized with R which is achieved at 80% conversion. System: Reactor Basis: 288.1 kmol/h of feed ( ) ( ) ( ) R = 69.8 kmol/h Then molar flow rates of each stream are calculated. Diagram and the results are shown in figure 5.1.1 and table 5.1.2. Normally 313.3kmol/h methanol enters the process. However amount of methanol that enters to the reactor is summed with recycle methanol. Figure 12.5.2.2: Diagram of the reactor 2CH3OH CH3OCH3 + H2O 1 3 2 4 5
  53. 53. 44 Table 12.5.2.3 : Explanation of symbols that used in diagram Symbol Streams 1 Methanol input the reactor 2 Water input to the reactor 3 Methanol leaving the reactor(unreacted) 4 DME leaving the reactor 5 Waste water leaving reactor Table 12.5.2.4 Molar flow rates of each stream Stream Flow rate(kmol/h) m1 279.2 m2 2.0 m3 56 m4 112 m5 159.1
  54. 54. 45  Reactor Feed Preparation Material Balance Firstly, feed preparation part was considered as a black box. By doing so, the overall energy that should be fed to the reactor inlet was calculated. n1=224.2 kmol/h n5=279.2 kmol/h n2=2.0 kmol/h n6=7.94 kmol/h T1=250 C T3=2500 C P1=1 bar P3=14.7 bar n3=55 kmol/h n4=5.94 kmol/h P2=13.5 bar T2=1210 C Figure 12.5.2.3: Flow diagram of feed preparation n1 : Methanol flow rate of stream 1 n2 : Water flow rate of stream 1 n3 : Methanol flow rate of stream 2 (recycle from reactor) n4 : Water flow rate of recycle n5: Methanol flow rate of stream 3 n6: Water flow rate of stream 3 P1 , P2 , P3 : Pressure values of stream 1, 2, 3 respectively T1, T2, T3 : Temperature values of stream 1, 2, 3 respectively Overall material balance by choosing system as whole feed preparation: n1 + n2 + n3+ n4= n5 + n6 (1) Feed Preparation1 2 3
  55. 55. 46 Balance on species of methanol and water will be as below since there is no reaction in feed preparation unit: n1 + n3 = n5 (2) n2+ n4= n6 (3) o Energy Balance By using those equations, flow rates of methanol and water in each stream were calculated and shown on the flow diagram. As it can be seen from the diagram, there is no unknown material around reactor. By knowing that values, an overall energy balance can be written as below: [In] – [Out] + [Generation] = [Accumulation] (4) ∑ Hin– ∑ Hout = Q + W (5) ∑ = Q + W (6) W = 0 (7) ∑ = Q (8) ∑ = Q =∫ ( ) ( ) ) ( ) ( ) ∫ (( ) ( ) ) (9) where [3] n1=224.2kmol/h; n2=2.0kmol/h; n3=55kmol/h; n4=5.94kmol/h n5=279.2kmol/h; n6=7.94kmol/h Heat capacities can be approximated by equations provided in the Perry’s Chemical Engineers handbook : Cp1 = a1 + b1·T + c1·T2 + d1·T3 (10) Cp2 = a2 + b2·T + c2·T2 + d2·T3 (11) a1=19.038 b1=0.09146 c1=-1.218*10-5 d1=-8.034*10-9 a2=29.163 b2=0.01449 c2=-0.202*10-5
  56. 56. 47 ΔHvap,water:Latent heat of vaporization of water =40.7 kJ/mol ΔHvap,meth:Latent heat of vaporization of meth =35.3 kJ/mol The values were also taken from Perry’s Chemical Enginners handbook and the data is interpolated to satisfy the current process. It is found that the mixture changes its phase at 427K and the second heat exchanger is required to heat the preheated mixture up to 523 K. Heat of vaporization for each specie is multiplied by flow rates in order to find overall latent heat. Plugging data into equation (9) and solving for : ∑ = Q =∫ ( ) ∫ ( ) 13.6404*106 kJ/h = 13640 MJ/h 13,640 MJ/h is required for heat exchangers to provide energy to heat the inlet materials to reactor at inlet temperature of 2500 C.This calculated value is very close to the obtained total heat duty from the ChemCad simulation, which is given as report in the Appendix section. Chemcad simulation is more reliable since it uses different algorithms into account therefore total heat is taken as the duty found in Chemcad as 12558.1 MJ/h and divided it into two heat exchangers ; as 10989 MJ/h for the first one and 1569 MJ/h for the second one. T1 = 318 K; T2 = 427 K; T3 = 523 K
  57. 57. 48 12.6 EQUIPMENT DESIGN FOR REACTOR AND REACTOR FEED PREPARATION Design of Reactor Synthesis of DME from methanol dehydration is catalytic reaction. So reactor is designed that it gives chance to use catalyst. Because of that reason a Packed Bed Reactor is chosen. Although PBR has difficulties with temperature control, it allows designer to get highest conversion per weight of catalyst of any catalytic reactor. Selection of catalyst is crucial at that point. The most important property of solid catalyst for gas phase reaction is physical structure of it because catalytic substance is usually located on the surface of the solid. Therefore, large surface areas of the catalyst are usually required to achieve the desired conversion. Large areas are obtained by using solids containing micropores and mesopores of the order of nanometer in size. Typically, these catalyst particles are made from more or less inert solids such as alumina, silica and alumina silicate. Hence amorphous alumina treated with 10% silica. Several assumptions are made and listed below in order to be able to design such a reactor. Assumptions; - Methanol is an ideal gas. - Standard heat of reaction is taken 298 o K. (Reference) - There are no side reactions. - Design temperature is assumed as 640 o K. - Design pressure is assumed 15 bar. - Single pass conversion is 0.8. - Maximum allowable internal pressure is 20 bar - Maximum working temperature is 4000 C since catalyst deactivates above that value.
  58. 58. 49 Approaching the problem The procedure listed below illustrates the design of the packed bed reactor for DME synthesis from methanol dehydration. Step 1.In order to design the reactor firstly type of reactor is decided. Since the reaction is a catalytic reaction, packed bed reactor is chosen. Step 2. Material balance around reactor: It is provided in the section 5.1 . Step 3. In order to find reactor outlet temperature and catalyst weight, design equation for PBR is applied. ( ) ( )( ) Step 4. Using catalyst weight, volume of reactor is calculated using bulk density of catalyst. Step 5. Using rule of thumb [1] for reactor design, cross-sectional area, length and diameter is determined. Step 6. Carbon steel (double-welded butt joints with spot examined) is chosen as a construction material of the reactor. Step 7. Thickness of reactor shell is calculated. ( )
  59. 59. 50 where; X : Single pass conversion FA0: Molar flow rate of methanol W: Weight of catalyst ΔHrxn : Heat of reaction Dp : Catalyst particle diameter D : Reactor diameter L: Length of reactor t: Thickness of reactor ri: Inside radius of shell before corrosion allowance is added S : Maximum allowable working stress Ej: Efficiency of joint expressed as a fraction P: Maximum allowable internal pressure Cc: Allowance for corrosion Calculations done for design of Packed Bed Reactor Equations (Eq. 6.1.1-1 and 6.1.1-2) used in order to design the reactor that is considered to be adiabatic, so convection term in Eqn. 6.1.1-2 is eliminated and becomes; ( )( )
  60. 60. 51 Where; ( ) ( ) ( ) ( ) Table 12.6.1 Parameters and its values Parameter Value k0(kmol/m3 .cat*h*kPa) 1.21*106 Ea (kJ/mol) 80.40 ΔHrxn -11770 Cp(methanol) 19.038 + 0.09146T - 1.218*10-5 T2 - 8.034*10-9 T3 Cp(water) 29.163 + 0.01449T – 0.202*10-5 T2 Cp(DME) 17.01+ 0.179T - 5.2*10-5 T2 - 1.9*10-9 T3 ρcatalyst(kg/m3 ) 700 CA and FA0 must be calculated in order to calculate weight of catalyst used. CA can be calculated using Ideal Gas Law. P*V = n*R*T Po*yA = CAo*R*To Where Po = 14.7 bar, yA = 0.995, To = 523.15 o K, R = 0.083 m3 *bar / kmol*K CA0 = 0.337 kmol/m3 Using Eq 6.1.1-1, Eq 6.1.2-1, Eq 6.1.2-2, Eq 6.1.2-3 and the values that is given in table 6.1.2.1, polymath code is written which is given in appendix 8.1. To achive 80% conversion of methanol, polymath gives the results as Toutlet = 638.65 K =365.50 o C W = 3350 kg From Eqn 6.1.1-3, volume of catalyst is calculated.
  61. 61. 52  = 4.80 m3 Then by using Eqn 6.1.1-4 and Eq 6.1.1-5, dimension of reactor is found. To apply this relations particle size should be decided. Since it is known that the dimension of catalyst particle size for fixed bed reactor is between 2-5 mm[3], it can be chosen as 3 mm. To determine this parameter, for some of diameter, length is calculated. Diameter is selected between 50 mm and 2000 mm. Calculated length are varied between 3332.5 m and 2.1 m. Then for practical usage, 0.7 m is selected for diameter. ( ) ( ( ) )  L=12.50 m Eqn. 6.1.1-7 is used for calculation of shell thickness of the packed bed reactor, carbon steel, double- welded butt joints with spot examined. Efficiency of joints of carbon steel material is given as 0.85 and designed temperature of the reactor is stated as 365.5 0 C. For carbon steel maximum allowable working stress is given as 827.37 bar. Also maximum allowable working pressure is 20 bar. For carbon steel corrosion allowance values are between 0.254 mm and 0.381 mm for a 10 years life [1]. So it is selected as 0.3175 mm. ( ) ( ) ( ) ( ) ( ) t = 10.44 mm = 0.01044 m
  62. 62. 53 Design of Reactor Feed Preparation Figure 12.6.1: CHEMCAD simulation for the feed preparation. Vessel (V-101) (Drum) From Table 11.6 in textbook [3] is being used while designing our vessel (V-101):  Liquid drums are usually horizontal:  Since our feed coming to vessel is in liquid phase, we choose our vessel as horizontal.  Knockout drums placed ahead of compressors should hold no less than 10 times the liquid volume passing per minute:  It is selected 15 times the liquid volume passing per minute which is 0.152 m3 /min in our system, so volume of our vessel is selected 2.28 m3 .  By using the optimum ratio of length to diameter, which is 3, D=1.0 m and L=3.0 m.
  63. 63. 54 Pump (P-101) According to design heuristics for pumps that is stated in table 11.9 [3], power for pumping liquids is determined by; W=(1.67)[Flow(m3 /min)][∆P(bar)]/ε Here, ε is the fractional efficiency which is equal to εsh as stated in Table 11.5. [3] The flow rate of stream which comes from the storage vessel is 9.12 m3 /h stream at 1bar and 25o C. And shaft efficiency is estimated as 0.45 from Table 11.9. [3] Following the heuristics; ( ⁄ ) ( ) ( ⁄ ) Then, drive efficiency is calculated by using the relation in Figure 8.7 in the textbook. For electric drive; ( ) ( ) ( ) ( ) ( ) ( ) ( ) (0.8424) Then drive power is calculated by; ( ) Heat Exchangers As it is shown in the procedure of DME production, pre-heating processes is achieved by two steps. In order to have more efficient heating process, firstly feed in liquid phase must be changed to gas phase, then it must be heated to the desired temperature. That is why two seperate heating processes is applied. Shell and tube heat exchanger is selected for each heating steps. Because the average temperature of the first heater is less than that of second heater, first one is operated at moderate pressure while the second is operated at high pressure. Equipment Selection – First Heat Exchanger Heat duty value for the first heat exchanger of feed preparation part can be found after doing the necessary balance calculations,. This value is estimated to be around 10988.72 MJ/h from the
  64. 64. 55 ChemCad simulation, which is given as report in the Appendix section. Then we can use the general heat exchanger equation 6.2.3.1.1. (6.2.3.1.1) Here, F is choosed as 1.0 since phase change is occuring. Also overall heat transfer coefficient, U, is taken as 280 W/m2 K, from table 11.11 [3] which is valid for liquid to liquid system. Water steam inlet is assumed as liquid at the high pressure for the heat exchanger. Figure 12.6.2: Schematic draw of the first heat exchanger We can write equation 6.2.3.1.2 to find logarithmic mean temperature difference and then we can find the overall area (A) of the heat exchanger. The first exchanger is designed to work with medium pressure steam. It is assumed that water steam enters the equipment at 250o C superheated steam and leaves as saturated and at 250o C. The latent heat of steam is used for feed heating. So, feed enters the exchanger at 45o C and leaves at 154o C. Superheated steam T= 250 o C Saturated steam T= 250 o C Feed Preparation Inlet T= 45o C Heated Feed T= 154o C First Heat Exchanger (Counter-Current & Shell- Tube)
  65. 65. 56 (6.2.3.1.2) Table 12.6.2: Description of the first heat exchanger streams and their temperatures Feed preparation inlet 45 o C Heated stream of the feed 154 o C Superheated steam inlet 250 o C Saturated steam outlet 250 o C ( ) ( ) Equipment Selection – Second Heat Exchanger For the second heat exchanger, which is used to heat the vapor mixture to reactor inlet temperature, same procedure is used. Heat duty value for the second heat exchanger of feed preparation section is estimated to be around 2030 MJ/h from the textbook [3] F is choosed as 0.9 since no phase change is occuring. Also overall heat transfer coefficient, U, is taken as 30 W/m2 K, which is valid for gas to gas systems.
  66. 66. 57 The second heat is exchanger is designed different than the first one. It uses reactor outlet for the heating fluidng. Hot reactor stream enters the equipment at 365.5 o C and it is assumed that it leaves at 250 o C. Figure 12.6.3: Schematic draw of the second heat exchanger Table 12.6.3: Description of the second heat exchanger streams and their temperatures Heated feed from 1st H.E. 154 o C Final stream from feed prep. 250 o C Hot stream from reactor outlet 365.5 o C Cooled stream of the reactor outlet 250 o C Hot reactor outlet T= 365.5o C Cooled reactor steam T= 250 o C Heated feed from 1st H.E. T= 154o C Final Stream T= 250o C Second Heat Exchanger (Counter-Current & Shell- Tube)
  67. 67. 58 ( ) ( ) According to Heuristics: (table 11.11)[3]  Due to boiling, pressure drop is chosen 0.1 bar for first heat exchanger. Also for other services, pressure drop is chosen 0.4 bar within the range of 0.2-0.62 bar.[3]  F is selected 1.0 for the first heat exchanger due to phase change and 0.9 for the second one. [3]  Overall heat transfer coefficient, U, is selected 280 W/m2 K which is applicable liquid to liquid systems (medium pressurized steam is liquid as well as feed) for the first exchanger and is selected 30 W/m2 K which is applicable for gas to gas systems for the second heat exchanger. [3]  Tubes are standard that have 1.9 cm OD, on a 2.54 cm triangle spacing, 4.9 m long for both exchangers. So first heat exchanger has340 tubes, and the second one has 728 tubes, approximately. [3]  Again due to heuristics, shell diameter of the first exchanger is calculated as 89cm, and the shell diameter of the second heat exchanger is calculated as 130cm, approximately. [3]
  68. 68. 59  Separation Columns: Separator Feed Preparation Condenser  Energy balance around Feed Preparation Condenser According to the CHEMCAD simulation, the heat duty required for condensation is 10274.8 MJ/hr. Then the amount of water required for cooling from 260 0 C to 90.7 0 C is calculated as shown below, 10274.8*1000 kJ/hr = m *4.18 kJ/kg. 0 C*(40-25) 0 C m = 163872 kg/hr = 9104 kmole/hr. ( ) ( ) ( ) ( ) = 127.7 0 C Q = U A F ΔTlm A = = = 26.29 m2 Feed= 282 kmole/hr T= 260 0 C P= 10.4 bar q= 1 XDME = 0.3968 XMethanol = 0.1979 Xwater =0.4053 Feed= 282 kmole/hr T= 90.7 0 C P= 10.4 bar q= 0.70 XDME = 0.3968 XMethanol = 0.1979 Xwater =0.4053
  69. 69. 60  Partial reboiler of DME separation column: The heat duty of the partial reboiler is taken from ChemCad DME Tower simulation, which is 3465.86 MJ/h. Overall heat transfer coefficient is taken as 1140 W/m2 .K due to boiling, and the correction factor as 1.0 since is a phase change occurs. In this case a high pressure steam of 41 bar at 252 0 C is used as utility. Steam out T = 180 0 C = undetermined Q = U A F ΔTlm 3465.86 MJ/h = (1140 W/m2 .K). A . (1) . (252 – 152) K (3465.86 * 10^6)/(3600) J/s = (1140 W/m2 .K). A. (1). (180 – 152) K A = 30.16 m2 ( ) = = 2032.76 kg/h Steam in T= 180 o C Saturated liquid T= 152o C Saturated vapor T= 152 o C Partial Reboiler
  70. 70. 61  Total condenser of DME separation column: The heat duty of the total condenser is taken from ChemCad DME Tower simulation, which is 4479.2 MJ/h. Overall heat transfer coefficient is taken as 850 W/m2 .k due to condensation and the correction factor is taken as 1.0 a phase change occurs. In this case low pressure steam is used as utility. ( ) ( ) ( ) ( ) = 12 0 C Q = U A F ΔTlm A = = = 122 m2 consumption rate of cooling water can be calculated from the following formula, Q = mwater* cp* ΔT mwater = ( ) = 71438.6 kg/hr  Partial reboiler of methanol separation column: The heat duty of the partial reboiler is taken from ChemCad methanol Tower simulation, which is 4275.5 MJ/h. Overall heat transfer coefficient is taken as 1140 W/m2 .K due to boiling, and the correction factor as 1.0 since is a phase change occurs. In this case a high pressure steam of 40 bar at250 0 C is used as utility. = undetermined Q = U A F ΔT 4275.5 MJ/h = (1140 W/m2 ). A . (1) . (250 – 180) 0 C (4275.5 * 10^6)/(3600) J/s = (1140 W/m2 .K). A. (1). (250 – 180) 0 C A = 14.88 m2 ( ) = = 2496 kg/h
  71. 71. 62  Total condenser of methanol separation column: The heat duty of the total condenser is taken from ChemCad DME Tower simulation, which is 4124.9 MJ/h. Overall heat transfer coefficient is taken as 850 W/m2 .K due to condensation and the correction factor is taken as 1.0 a phase change occurs. In this case low pressure steam is used as utility. ( ) ( ) ( ) ( ) = 106.32 0 C Q = U A F ΔTlm A = = = 12.68 m2 consumption rate of cooling water can be calculated from the following formula, Q = mwater* cp* ΔT mwater = ( ) = 65787.87 kg/h  Wastewater cooler from the bottom of methanol tower: The wastewater from the bottom of methanol tower is cooled from 191 0 C to 40 0 C by using a heat exchanger. A chemcad simulation is conducted to estimate the heat duty that is 1386.17MJ/h. Overall heat transfer coefficient is taken as 850 W/m2 .K because a phase change occurs l. The correction factor is taken as 0.9 as there is no phase change occurs. ( ) ( ) ( ) ( ) = 55.96 0 C Q = U A F ΔTlm A = = = 43.6 m2 consumption rate of cooling water can be calculated from the following formula, Q = mwater* cp* ΔT mwater = ( ) = 23492.2 kg/hr
  72. 72. 63  DESIGN OF DISTILLATION TOWERS i) DME Tower Stage Calculations There are two distillation columns necessary for the dimethyl ether production from methanol dehydration. In this process, first one is called DME Tower and DME is taken as top product and remaining methanol-water mixture is sent to the second column, which is Methanol Tower. Number of stage calculations for the first tower is carried out by Shortcut Method and method of attack is given as below; Method of Attack: 1) Identify the properties of inlet and outlet streams such as flow rate, composition, temperature, pressure and feed condition (q). 2) Indicate the distillation system as multicomponent and selecting light key as methanol and heavy key as water. 3) Using SCDS column profile (appendix) obtained from Chemcad relative volatility for light key (DME) is calculated with respect to heavy key (methanol) and average volatility is found by equation X.5.1 : √ 4) For multicomponent system the minimum number of stages (Nmin) is calculated by Fenske equation X.5.2: ( )( ) ( ) 5) Taking into account CMO and constant relative volatilities ( = ̅̅̅̅̅̅̅̅ ), Underwood equation (X.5.3) will be used to calculate : (Wankat,2011, p251) ( ) ∑ 6) Determine the minimum reflux ratio (Rmin ) using both graphical method and Underwood equation (Wankat,2011, p250) : ∑
  73. 73. 64 7)Then, the reflux ratio (R) is calculated ,in both ways, at the pinch point which is the intersection point of q-line and rectifying section operating line on the equilibrium line of methanol. The second way to calculate Reflux ratio is to use thumb rule taking ratio of ⁄ as 1.3 .  Operating line for rectifying section: yn+1 = ( ) ( ) ( )  Operating line for feed stream: yn+1 = ( ) ( ) ( )  Operating line for stripping section: Ym+1 = ( ) ( ) ( ) Determine R using the common relation between R and Rmin which is;  (1.2)R min< R < (1.5)Rmin 8) Again using operating lines of each sections, determine theoretical stages by graphical method.
  74. 74. 65 Theoretical stage number ,N, will also be calculated by Kirkbride equation : 6) Determine overall efficiency of column using O’Connell’s correlation :  E0 = 51-(32.5*log(µa αa) Where; µa is the average liquid viscosity estimated at the average column temperature and αa is the average relative volatility of light key to the heavy key 7) Using overall efficiency, determine actual number of stage.  E0 = * 100 ii) DME Tower Diagram Figure 12.6.4 : Block diagram for the DME Tower 1) System is defined as in the Figure 11.5.1 q value is found as 0.704 from ChemCad simulation (SCDS Simulation) D = 112 kmole/hr T= 47.7 0 C P= 10.4 bar q = 0 XDME = 0.996 XMethanol = 0.0043 Xwater = ~ 0 Feed= 281 kmole/hr T= 90.7 0 C P= 10.4 bar q= 0.704 XDME = 0.397 XMethanol = 0.198 Xwater =0.405 B = 169.5 kmole/hr T= 152 0 C P= 10.4 bar Vapor fraction = 0.0 XDME = 0.00147 XMethanol = 0.326 Xwater =0.673
  75. 75. 66 2) Light Key (LK) is selected as DME Heavy Key (HK) is selected as Methanol 3) Relative volatilities with respect to stage number were obtained by Chemcad .(Appendix) Relative volatilities of light key for top and bottom stages are as follows: ; √ 4) ( )( ) ( ) ( )( ) ( ) 5) ; ( ) value was calculated by trial-error method .The root that was found is valid and reasonable since the value is in between the volatilities of heavy and light key. 6) ∑ 7) 8) ⁄ ; ⁄
  76. 76. 67 Plugging computed data into Gilliland correlation (Wankat,2011) and solving for N Figure 12.6.5.Gillilan correlation (1968 , McGraw-Hill) 9) Solving for feed location using Kirkbride equation (X.5.5). ( ) ( ) ( ) ( ) Feed tray is found as 4th tray. Both stage number and feed stage number is consistent with the Chemcad simulation and exactly these numbers were found by short-cut method calculation and simulation.
  77. 77. 68 10) √ 11)
  78. 78. 69 ii) Methanol Tower Stage Calculations In methanol tower which is the second separation unit of the dimethyl ether production from methanol dehydration, methanol is taken as a top product and water is taken as bottom product. To make these calculations, some assumptions are made. These are;  Binary mixture system  Recovery of methanol is 96%  Recovery of water is 99%  Design pressure of column is 10.4 bar  Constant molar overflow throughout the column.  Number of stage calculations for the second tower is carried out by McCabe-Thiele method and method of attack is given as below; Method of Attack: 1) Identify the properties of inlet and outlet streams such as flow rate, composition, temperature, pressure and feed condition (q). 2) Indicate the distillation system select light key as methanol and heavy key as water. 3) Determine the minimum reflux ratio (Rmin ) using graphical method. Then, the reflux ratio (R) is calculated at the pinch point which is the intersection point of q-line and rectifying section operating line on the equilibrium line of methanol.  Operating line for rectifying section: yn+1 = ( ) ( ) ( )  Operating line for feed stream: yn+1 = ( ) ( ) ( )  Operating line for stripping section:
  79. 79. 70 Ym+1 = ( ) ( ) ( ) 4) Determine R using the common relation between R and Rmin which is;  (1.2)R min< R < (1.5)Rmin 5) Again using operating lines of each sections, determine theoretical stages by graphical method. 6) Determine overall efficiency of column using O’Connell’s correlation.  E0 = 51-(32.5*log(µa αa) 7) Using overall efficiency, determine actual number of stage.  E0 = * 100 Figure 12.6.6 : Block diagram for the DME Tower Feed= 169.5 kmole/hr T= 152 0 C P= 10.4 bar q= 1 XDME = 0.0002 XMethanol = 0.327 Xwater =0.672 D = 55 kmole/hr T= 139 0 C P= 10.4 bar q = 1 XDME = 0.0005 XMethanol = 0.995 Xwater =0.000 B = 114.5 kmole/hr T= 181 0 C P= 10.4 bar Vapor fraction = 0.0 XDME = 0.0 XMethanol = 0.0012 Xwater =0.9988
  80. 80. 71 Calculation of ideal stages: The number of ideal stages for methanol water separation is determined by using McCabe- Thiele method. The equilibrium data of methanol at 10.4 bar is obtaind from CHEMCAD simulation. Firstly, Rmin is calculated at the pinch point which is the intersection point of rectifying op.line and q-line at the equilibrium line as it is seen in figure. Since the feed is saturated liquid, q =1. = 0.442 Rmin = 1.251 The actual operating reflux ratio (R) is calculated using the relation below. 1.2 Rmin< R <1.5 Rmin So, R is found as 1.625 Secondly, operating line equations for the methanol separation column are found as it is illustrated below, Rectifying Section: The operating line is yn+1 = ( ) ( ) ( ) Hand Drawn is provided on the next page. Stripping section Stripping section Rectifying section
  81. 81. 72 Point 1. at = so, yn+1 = = 0.995 Point 2. at = 0 so, , yn+1 = ( ) = 0.379 Using these two points, the operating line for rectifying can be drawn. Feed Section: The operating line is yn+1 = ( ) ( ) ( ) At x = xfeed = 0.327 so, yn+1 = = 0.327 In fact, q of the methanol separation column is ( q = 1) that is a saturated liquid. Stripping Section: The operating line is Ym+1 = ( ) ( ) ( ) At = so, Ym+1 = = 0.0012 Now using these information from the three sections, number of stages can be determined as it is drawn in the figure. Number of ideal stage is calculated as 22 21 stages + 1 reboiler The stage number is directly proportional to the purification of methanol.99.5% mole of methanol is recycled and 99.8% mole is taken waste. Taking into consideration the environmental aspects the design is optimized to give the least mole percentage of methanol in waste water. The overall column efficiency is determined using O’Connell’s correlation. Average temperature of the bottom and top streams is calculated as 145.50 C.The terms µa and αa are calculated at the average temperature. Average relative volatility is 0.304 and individual viscosity values are as 0.194 and 0.184. The average viscosity is calculated as : ( ) ( ) ( ) ( ) ( ) ( ) Substituting these values into O’Connell’s correlation, overall efficiency is found as : THE HAND DRAWN is provided in the next page
  82. 82. 73 12.7 Cost Calculations including Equipment Cost Data ECONOMIC ANALYSIS FOR PUMPS Now, purchased equipment cost can be obtained by using the equation A.1 in the textbook ( ) ( ( )) ( ) where A is shaft power. By using Table A.1, equipment cost data in textbook and substituting k1, k2 and k3 values into eqn. 6, purchased equipment cost can be obtained for pump 1 as following: ( ) ( ( )) By substituting equipment cost data in the textbook into eqn.6, purchased equipment cost can be obtained for pump 2 as following: ( ) ( ( )) By substituting equipment cost data in the textbook into eqn.6, purchased equipment cost can be obtained for pump 3as following: ( ) ( ( ))
  83. 83. 74 Utility Cost Estimation for Pumps All pumps are working with electricity. The price of electricity is given as 0.11 $/kwh. Then, annual electricity cost will be found for each pump by the following procedure; Where; Celect is the annual electricity cost P is the power of the pump t is the annual working time of pump, 8320 h/year Pr is the price of electricity, 0.11 $/kwh Then, the following table shows the electricity cost for each pump; Pumps Power (kW) Celect ($/year) P-201A/B 8.17 7413 P-202A/B 2.16 1977 P-203A/B 9.48 8676 DISTILLATION TOWERS CAPCOST program is used for finding the equipment costs of the towers. The required parameters are taken from the previous progress report as; Table1 Parameters of separation columns Column 1 (T-101) Column 2 (T-102) Diameter (m) 0.76 0.76
  84. 84. 75 Height (m) 6.22 18.9 P (bar) 10.4 10.4 Material of Construction Carbon Steel Carbon Steel Tray type sieve sieve No. of trays 7 28 Purchased equipment costs of towers found as followed; Table2Purchased equipment costs of towers from CAPCOST Towers Tower Description Height (meters) Diameter (meters) Tower MOC Pressure (barg) Purchased Equipment Cost T-101 36 Carbon Steel Sieve Trays 6.22 0.76 Carbon Steel 10.4 10,700 $ T-102 30 Carbon Steel Sieve Trays 18.9 0.76 Carbon Steel 10.4 35,000 $ REACTOR Reactor is taken as pressurized vessel. CAPCOST program is used also for finding the equipment cost of the reactor. The required parameters are taken from the previous progress report as; Diameter (m) 0.72 Height (m) 12.5 P (bar) 14.7 Material of Construction Carbon Steel
  85. 85. 76 Purchased equipment cost of reactor found as followed; Table3 Purchased equipment cost of reactor from CAPCOST Vessels Orientation Length/Height (meters) Diameter (meters) MOC Pressure (barg) Purchased Equipment Cost R-101 Vertical 12.5 0.72 Carbon Steel 14.7 7,376 $ Utility Cost for Reactor The silica-alumina (zeolite zsm-5) catalyst, which is used in the reactor, is planned to be changed annualy. The cost of the catalyst is considered as a utility cost. The unit price of the catalyst is found as 18 $/kg. The required amount of catalyst for one year can be calculated by using volume of the packed-bed section of the reactor and the bulk density of the catalyst. , where, , , And the annual cost of the catalyst is found as; REFLUX DRUMS There are two reflux drums for each separation column’s condenser section. These drums are relatively small vessels. From the heuristics for towers, reflux drums are horizantal with a liquid holdup of 30 min half full [1]. The required parameters for CAPCOST program are found as followed; First the volume of drums are found;
  86. 86. 77 For Drum 1 (V-103) For Drum 2 (V-104) By taking length/diameter ratio as 3 from heuristics, founded diameter and height shown in the table below; Table4 Parameters of drums Drum 1 (V-103) Drum 1 (V-104) Diameter (m) 1.48 0.97 Height (m) 4.44 2.91 P (bar) 10.4 10.4 Material of Construction Carbon Steel Carbon Steel From CAPCOST, purchased equipment costs of drums are found as followed; Table5 Purchased equipment costs of drums from CAPCOST Vessels Orientation Length/Height (meters) Diameter (meters) MOC Pressure (barg) Purchased Equipment Cost V-103 Horizontal 4.44 1.48 Carbon Steel 10.4 9,130 $ V-104 Horizontal 2.91 0.97 Carbon Steel 10.4 4,920 $
  87. 87. 78 VESSELS In our plant we need equipment for storage. Vessels are used to meet this need. For the feed part, if there is something wrong with the flow of methanol, methanol stored in the vessels will be sent to the reactor and keeps the operation going. For the outlet part produced DME should be stored if it cannot be saled as soon as it comes out. We need those vessels for the storage of one day so calculations for the volume of the vessels done accordingly. Methanol Storage Vessel We need the volumetric flow rate of methanol per day to find the vessel volume needed. Volumetric flow rate of methanol is found by dividing its mass flow rate to its density. Density is taken from chemcad results. Since it is the daily flow rate, it is equal to the capacity of the vessel. V101=220 m3 From the heuristics,
  88. 88. 79 DME Storage Vessel DME produced per day is calculated from material balance and found as, Volumetric flow rate of methanol is found by dividing its mass flow rate to its density. Density is taken from chemcad results. Since it is the daily flow rate, it is equal to the capacity of the vessel. V105=183.56 From the heuristics, Storage vessels’ costs are found from CAPCOST program:
  89. 89. 80 Vessels Orientation Length/Height (meters) Diameter (meters) MOC Pressure (barg) Purchased Equipment Cost V-101 Vertical 13.6 4.53 Carbon Steel 2 145,000 $ V-105 Vertical 12.8 4.27 Carbon Steel 2 124,000 $ COST CALCULATIONS INCLUDING EQUIPMENT COST DATA RATE OF RETURN ON INVESTMENT Rate of return on investment (ROROI) represents the nondiscounted rate at which money is made from the fixed capital investment.  Net Annual Earnings = (Gross Profit-SARE expenses)*(1-Income Taxes)  SARE expenses = 0.1*Gross Sales  Gross Profit = Gross Sales –Total Manufcturing Cost  Total Fixed Capital Investment = Total Manufacturing Capital + Non-Manufacturing Capital  Total Manufacturing Capital = Purchase Equipment Cost * Lang factor Lang factor=4  Non-Manufacturing Capital = 0.25* Total Manufacturing Capital  Working Capital = 0.03*Total Manufacturing Capital+0.10*Gross Sales+0.50*Raw Material Inventory+0.50*Finished Product Inventory
  90. 90. 81 Table6 Utilities Cost Data Steam High Pressure (40 bar g, sat) 16.50 $/mt Medium Pressure (10 bar g, sat) 14.00 $/mt Low Pressure (4 bar g, sat) 12.50 $/mt Electricity 0.11 $/kwh Cooling Water 15.00 $/1000 m3 Manufacturing cost factors Labor Wage Rate 15.00 $/year Supervision Salary Rate 4000 $/month Payroll Charges 35% of labor and supervision Repairs 6% of Mfg.Cap/year Factory Supplies Assume 2%of Mfg.Cap/year Laboratory Product Control Technical Service Royalty Depreciation 8% of Mfg.Cap/year Factory İndirect Expense (Property Taxes, Insurance, Other Distrbutable Expenses) 4% of Mfg.Cap/year
  91. 91. 82 ECONOMIC ANALYSIS All the equipment costs are added for the total equipment cost (based on the equipment cost list), Total Equipment Cost= 1058046 $ By using Lang Factor for calculation of total cost, Taking Lang factor as 4.0 Total Manufacturing Capital=1058046 $ * 4.00 = 4232184 $/year If the contingency was considered as 10% of Total Manufacturing Capital, then Total Manufacturing Cost Estimate was found; Contingency 4232184 $* 10% =423218 $ TMC estimate : 4232184 $ + 423218 $= 4655402 $ (which is 1.1 of Total manufacturing cap) Additionally, Non-Manufacturing Capital Investment was evaluated as 25% of Total Manufacturing Capital. Non-manufacturing Fixed Capital Investment (NMFCI) = 4232184 * 0.25=805578 $ Fixed Capital investment (FCI)=TMC+NMFCI=4655402 $ + 805578 $= 5,460,980 $ Price of methanol=0.22$/kg Store supplies were given as 3% of Total Manufacturing Capital. Then, Store supplies=0.03 * 4232184=12696 $ Gross sales= $ 42865000 All other items=42865000 * 0.1=4286500 $ Working Capital ( ) Working Capital= 0.03*4232184+0.1*42865000+12862504+13500=17,289,470 $
  92. 92. 83 Thus, manufacturing capital is calculated by summing up fixed capital and working capital as given below : MC=17,289,470 $ + 5,460,980 $= 22,750,450 $ Total MANUFACTURING COST ESTIMATION Labor and Supervision Cost Manufacturing cost consists of labor, supervision, repairs , factory supplies, laboratory, product control, technical service, royalty, factory indirect expenses and depreciation. Labor A correlation is used to find the number of workers in the plant. NOL=(6.29+31.7p +0.23Nnp)0.5 Nnp=1 reactor+2 columns+4 heat exchangers Nnp=7 NOL=(6.29+0.23x7)0.5 =2.81 Plant operates 24h/day 365days/year therefore, Total operation hour=365x24=8760 h/year A worker works 8 hours a day 6 days a week and 48 weeks a year, therefore; Working hour of a worker in a year=8hours/dayx6days/weekx48weeks/year=2304 h/year Number of workers= (8760h/year/2304h/year)x2.81=10.68≈11workers Wage Rate=15.00$/h Labor Cost=11x15.00$/hx2304h/year=380160$/year Supervision We need engineers as well as workers in our plant. Number of engineers can be assumed as 1/3rd of number of workers, therefore; Number of engineers in the plant =11/3=3.67≈4 engineers Supervision cost= 4000 USD/month x 4 x 12=192000 $/year
  93. 93. 84 Payroll charges It will be 35% of Labors and Supervision factor. Payroll ch= (380160+192000) *0.35=200256 $/year Repair factors Assuming it constitutes 2 % of Mfg. Cap./year : Repair fac=4232184 $ * 0.02= 84644$/year Depreciation (Straight Line) By depreciating equipment cost for ten straight years: Depreciation=Equipment cost/10 years= 1058046/10=105805 $/year Factory Indirect Expense FIE=4232184 $ * 0.08=169287$/year Hence, sum of all these gives the total manufacturing cost. Total Manufacturing Cost =Raw material inventory + Total utility cost + Labor cost + Supervision+ Payroll expenses + Repairs cost + Product control cost +Depreciation +Indirect expenses ANNUAL EARNINGS AND RETURN Price of DME= 1$/kg Produced DME in ton : 112kmol/hr * 0.046 ton/kmol* 8320 days/hr=42,865 ton Gross profit=Sales revenue – Manufacturing cost GP= Until that point, Sales-Administration-Research-Engineering expenses are not covered by any of the previous percentage factors. To determine net gross profit, SARE expenses is taken 10% of annual income than subtracted from gross profit to find net gross profit. ( ) To calculate the income tax, tax rate is taken 20%. ( )
  94. 94. 85 ROI=27% 12.8. Polymath program needed for calculation of catalyst weight and reactor outlet temperature. d(X)/d(W) = (-rA / r) / Fa0 X(0) = 0 d(T)/d(W) = (rA / r) * Hrxn / (Cpa * Fa0) T(0) = 523.15 r = 700 # density of the catalyst Fa0 = 288.13 # kmol/h rA = -k * exp(-Ea / (R * T)) * Ca * R * T Ea = 80480 Ca = Ca0 * (1 - X) * (523.15 / T) Ca0 = 0.337 # kmol/m3 R = 8314e-3 k = 1210000 Hrxn = -11770 + (8097e-3 + 11e-3 * T - 2966e-8 * T ^ 2 + 1417e-11 * T ^ 3) * (T - 298) Cpa = (19038e-3) + (9146e-5) * T - (1218e-8) * T ^ 2 - (8034e-12) * T ^ 3 W(0) = 0 W(f) = 3350
  95. 95. 86
  96. 96. 87
  97. 97. 88 8.2. ChemCad Report for the Heat Exchangers CHEMCAD 6.3.1 Simulation: First Heat Exchanger Date: 12/16/2013 Time: 18:21:24 EQUIPMENT SUMMARIES Heat Exchanger Summary Equip. No. 1 Name 1st Stream dp bar 0.1000 1st Stream T Out C 155.0000 Calc Ht Duty MJ/h 10998.7197 LMTD Corr Factor 1.0000 1st Stream Pout bar 15.3000 CHEMCAD 6.3.1 Simulation: Second Heat Exchanger Date: 12/16/2013 Time: 18:27:29 EQUIPMENT SUMMARIES Heat Exchanger Summary Equip. No. 1 Name 1st Stream dp bar 0.4000 1st Stream T Out C 250.0000 Calc Ht Duty MJ/h 1569.3738 LMTD Corr Factor 1.0000 1st Stream Pout bar 14.7000
  98. 98. 89
  99. 99. CHEMCAD 6.3.1 Page 1 Simulation: Full_Scheme_DME_Simulation Date: 05/21/2014 Time: 15:45:17 STREAM PROPERTIES Stream No. 1 2 3 4 Name feed - - Overall - - Molar flow kmol/h 226.0020 226.0020 281.4517 281.4517 Mass flow kg/h 7213.5295 7213.5295 8985.1616 8985.1616 Temp C 25.0000 25.7216 110.8411 250.0000 Pres bar 1.0000 15.5000 15.2000 15.1000 Vapor mole fraction 0.0000 0.0000 0.0000 1.000 Enth MJ/h -54097. -54084. -65149. -54567. Tc C 240.1335 240.1335 240.0204 240.0204 Pc bar 81.4581 81.4581 81.3963 81.3963 Std. sp gr. wtr = 1 0.801 0.801 0.801 0.801 Std. sp gr. air = 1 1.102 1.102 1.102 1.102 Degree API 45.0671 45.0671 45.1014 45.1014 Average mol wt 31.9180 31.9180 31.9243 31.9243 Actual dens kg/m3 790.3986 789.7075 697.2007 11.8008 Actual vol m3/h 9.1264 9.1344 12.8875 761.4013 Std liq m3/h 9.0012 9.0012 11.2141 11.2141 Std vap 0 C m3/h 5065.5286 5065.5286 6308.3585 6308.3585 - - Vapor only - - Molar flow kmol/h 281.4517 Mass flow kg/h 8985.1616 Average mol wt 31.9243 Actual dens kg/m3 11.8008 Actual vol m3/h 761.4013 Std liq m3/h 11.2141 Std vap 0 C m3/h 6308.3585 Cp kJ/kg-K 1.9222 Z factor 0.9393 Visc N-s/m2 1.753e-005 Th cond W/m-K 0.0431 - - Liquid only - - Molar flow kmol/h 226.0020 226.0020 281.4517 Mass flow kg/h 7213.5295 7213.5295 8985.1616 Average mol wt 31.9180 31.9180 31.9243 Actual dens kg/m3 790.3986 789.7075 697.2007 Actual vol m3/h 9.1264 9.1344 12.8875 Std liq m3/h 9.0012 9.0012 11.2141 Std vap 0 C m3/h 5065.5286 5065.5286 6308.3585 Cp kJ/kg-K 2.5399 2.5440 3.2792 Z factor 0.0022 0.0333 0.0290 Visc N-s/m2 0.0005406 0.0005409 0.0002388 Th cond W/m-K 0.2007 0.2005 0.1764 Surf. tens. N/m 0.0223 0.0223 0.0145 CHEMCAD 6.3.1 Page 2 Simulation: Full_Scheme_DME_Simulation Date: 05/21/2014 Time: 15:45:17 STREAM PROPERTIES Stream No. 5 6 7 8 Name - - Overall - -
  100. 100. Molar flow kmol/h 281.4525 281.4525 281.4519 169.5254 Mass flow kg/h 8985.1900 8985.1900 8985.1608 3835.7481 Temp C 340.9631 259.7677 100.0000 152.4593 Pres bar 13.9000 13.9000 13.9000 10.4000 Vapor mole fraction 1.000 1.000 0.2563 0.0000 Enth MJ/h -54566. -56123. -65403. -44026. Tc C 204.0864 204.0864 204.0867 309.8234 Pc bar 44.9646 44.9646 44.9645 129.2361 Std. sp gr. wtr = 1 0.753 0.753 0.753 0.896 Std. sp gr. air = 1 1.102 1.102 1.102 0.781 Degree API 56.3859 56.3859 56.3858 26.4668 Average mol wt 31.9244 31.9244 31.9243 22.6264 Actual dens kg/m3 8.8889 10.4274 60.1097 758.4805 Actual vol m3/h 1010.8312 861.6876 149.4794 5.0571 Std liq m3/h 11.9307 11.9307 11.9306 4.2821 Std vap 0 C m3/h 6308.3762 6308.3762 6308.3638 3799.6823 - - Vapor only - - Molar flow kmol/h 281.4525 281.4525 72.1304 Mass flow kg/h 8985.1900 8985.1900 3151.7115 Average mol wt 31.9244 31.9244 43.6947 Actual dens kg/m3 8.8889 10.4274 22.4123 Actual vol m3/h 1010.8312 861.6876 140.6244 Std liq m3/h 11.9307 11.9307 4.6140 Std vap 0 C m3/h 6308.3762 6308.3762 1616.7046 Cp kJ/kg-K 2.2158 2.0503 1.6601 Z factor 0.9778 0.9606 0.8736 Visc N-s/m2 2.024e-005 1.770e-005 1.223e-005 Th cond W/m-K 0.0548 0.0439 0.0262 - - Liquid only - - Molar flow kmol/h 209.3216 169.5254 Mass flow kg/h 5833.4490 3835.7481 Average mol wt 27.8684 22.6264 Actual dens kg/m3 658.7736 758.4805 Actual vol m3/h 8.8550 5.0571 Std liq m3/h 7.3167 4.2821 Std vap 0 C m3/h 4691.6595 3799.6823 Cp kJ/kg-K 3.3380 4.0685 Z factor 0.0207 0.0116 Visc N-s/m2 0.0002071 0.0001792 Th cond W/m-K 0.1853 0.3153 Surf. tens. N/m 0.0101 0.0212 CHEMCAD 6.3.1 Page 3 Simulation: Full_Scheme_DME_Simulation Date: 05/21/2014 Time: 15:45:17 STREAM PROPERTIES Stream No. 9 10 11 12 Name DME waste water - - Overall - - Molar flow kmol/h 111.9265 281.4517 114.0757 55.4497 Mass flow kg/h 5149.4123 8985.1616 2064.1150 1771.6326 Temp C 47.7170 154.0000 180.4249 138.4342 Pres bar 10.4000 15.1000 10.4000 10.4000 Vapor mole fraction 1.000 1.000 0.0000 1.000 Enth MJ/h -20571. -56123. -31202. -11065. Tc C 127.2906 240.0204 372.7922 239.5604 Pc bar 53.6864 81.3963 218.7304 81.1443
  101. 101. Std. sp gr. wtr = 1 0.673 0.801 0.998 0.801 Std. sp gr. air = 1 1.589 1.102 0.625 1.103 Degree API 78.6722 45.1014 10.3527 45.2413 Average mol wt 46.0071 31.9243 18.0943 31.9503 Actual dens kg/m3 21.0511 15.7549 881.9093 10.8465 Actual vol m3/h 244.6153 570.3085 2.3405 163.3364 Std liq m3/h 7.6485 11.2141 2.0693 2.2129 Std vap 0 C m3/h 2508.6812 6308.3585 2556.8517 1242.8299 - - Vapor only - - Molar flow kmol/h 111.9265 281.4517 55.4497 Mass flow kg/h 5149.4123 8985.1616 1771.6326 Average mol wt 46.0071 31.9243 31.9503 Actual dens kg/m3 21.0511 15.7549 10.8465 Actual vol m3/h 244.6153 570.3085 163.3364 Std liq m3/h 7.6485 11.2141 2.2129 Std vap 0 C m3/h 2508.6812 6308.3585 1242.8299 Cp kJ/kg-K 1.4982 1.6854 1.6468 Z factor 0.8521 0.8617 0.8953 Visc N-s/m2 1.046e-005 1.446e-005 1.381e-005 Th cond W/m-K 0.0200 0.0312 0.0286 - - Liquid only - - Molar flow kmol/h 114.0757 Mass flow kg/h 2064.1150 Average mol wt 18.0943 Actual dens kg/m3 881.9093 Actual vol m3/h 2.3405 Std liq m3/h 2.0693 Std vap 0 C m3/h 2556.8517 Cp kJ/kg-K 4.3973 Z factor 0.0077 Visc N-s/m2 0.0001477 Th cond W/m-K 0.6638 Surf. tens. N/m 0.0413 CHEMCAD 6.3.1 Page 4 Simulation: Full_Scheme_DME_Simulation Date: 05/21/2014 Time: 15:45:17 STREAM PROPERTIES Stream No. 13 Name - - Overall - - Molar flow kmol/h 281.4519 Mass flow kg/h 8985.1599 Temp C 90.6595 Pres bar 10.4000 Vapor mole fraction 0.2969 Enth MJ/h -65403. Tc C 204.0868 Pc bar 44.9646 Std. sp gr. wtr = 1 0.753 Std. sp gr. air = 1 1.102 Degree API 56.3858 Average mol wt 31.9243 Actual dens kg/m3 39.7213 Actual vol m3/h 226.2054 Std liq m3/h 11.9306 Std vap 0 C m3/h 6308.3638
  102. 102. - - Vapor only - - Molar flow kmol/h 83.5497 Mass flow kg/h 3651.7291 Average mol wt 43.7073 Actual dens kg/m3 16.7073 Actual vol m3/h 218.5706 Std liq m3/h 5.3457 Std vap 0 C m3/h 1872.6537 Cp kJ/kg-K 1.6317 Z factor 0.8996 Visc N-s/m2 1.179e-005 Th cond W/m-K 0.0247 - - Liquid only - - Molar flow kmol/h 197.9022 Mass flow kg/h 5333.4308 Average mol wt 26.9498 Actual dens kg/m3 698.5734 Actual vol m3/h 7.6347 Std liq m3/h 6.5850 Std vap 0 C m3/h 4435.7101 Cp kJ/kg-K 3.3462 Z factor 0.0150 Visc N-s/m2 0.0002354 Th cond W/m-K 0.2072 Surf. tens. N/m 0.0137

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